Chapter 6-Mature B Cell Neoplasms

Definition

• Clonal proliferations of B cells: naive B cells to mature plasma cells

• Recapitulate stages of normal differentiation
Epidemiology

• >90% of lymphoid neoplasms worldwide; annually 4% of all cancers

• More common in developed countries

• Annual incidence 15/100,000 (USA)

• Follicular lymphoma & DLBCL (50% of NHL) and plasma cell myeloma are most common

• In USA, B cell neoplasms account for >70,000 new cases per year; 6% of all cancers

• Geographic variations:

– Follicular lymphoma (10% NHL in USA)

– Burkitt lymphoma (equatorial Africa)

• Median age for all types: 60’s and 70’s

• Gender predilection: overall M>F

– Exceptions: follicular lymphoma (F=58%), and mediastinal LBCL (F=66%)

• Risk factors:

» immunosuppression (DLBCL and Burkitt)

» autoimmune disease (MALT lymphoma)

Chronic Lymphocytic Leukemia (CLL) /

Small Lymphocytic Lymphoma (SLL)

Definition

• Neoplasm of monomorphic small, round B lymphocytes in blood, BM and lymph nodes, admixed with prolymphocytes and paraimmunoblasts (pseudofollicles), usually expressing CD5 and CD23.

• SLL is restricted to non-leukemic cases

Epidemiology

• Comprises 90% of chronic lymphoid leukemias in USA and Europe

• 6.7% of non-Hodgkin´s lymphoma

• Majority of patients >50 y (median 65)

• M:F ratio 2:1

Sites of involvement

• CLL by definition, BM and PB (lymphocyte count > 10x10⁹/L)

• Can be diagnosed with lymphocyte count < 10x10⁹/L with proper morphology and immunophenotype

• Lymph nodes, liver and spleen are typically infiltrated

• Skin, breast and ocular adnexae may be involved

Clinical features

• Most patients are asymptomatic

• Some may present with fatigue, autoimmune hemolytic anemia, infections, splenomegaly, hepatomegaly, lymphadenopathy or extranodal infiltrates

• Small M-component in some patients

Morphology

· CLL cells are small lymphocytes with clumped chromatin and scant cytoplasm clear to basophilic with regular outline

· Smudge or basket cells are typically seen in the blood

· Proportion of prolymphocytes in the smear usually < 2%. Increasing numbers correlate with more aggressive disease, p53 abnormalities and trisomy 12.

· CLL with increased prolymphocytes (CLL/PL) defined by prolymphocytes >10% but <55%

· BM involvement can be interstitial, nodular or diffuse or combinations

· Pseudofollicles less common in BM

· Paratrabecular aggregates not typical

· Nodular and interstitial patterns are seen in early disease

· Diffuse pattern associated with advanced disease and BM failure

· Transformation to diffuse large B-cell lymphoma (Richter syndrome) is characterized by confluent sheets of large cells that may resemble paraimmunoblasts, but are more often centroblast- or immunoblast-like.

· CLL may be associated with Hodgkin lymphoma, with scattered R-S cells and variants in a CLL background or as discrete areas of classic HL.

Immunophenotype

• Express weak or dim surface IgM or IgM and IgD, CD5, CD19, CD20 (weak), CD22 (weak), CD79a, CD23, CD43, CD11c (weak)

• CD10-, cyclin D1-

• As a rule, FMC7 and CD79b negative or weak

• Cases with unmutated Ig variable region genes are reported to be CD38+

• Antigen specificity of sIg frequently is against self antigens. These Abs often have broad specificity (cross-reactive idiotypes)

• Cytoplasmic Ig is detectable in about 5% of the cases

• CD5 and CD23 are useful in distinguishing from mantle cell lymphoma (MCL). Rarely CLL is CD23-. Rarely MCL is CD23+. Cyclin D1 is useful for CD5+, CD23- cases to rule out MCL.

• Some cases with typical CLL morphology may have a different immunophenotype (CD5- or CD23-, FMC7+ or CD11c+, or strong sIg, or CD79b+)

Genetics

• Antigen receptor genes: Ig heavy and light genes are rearranged. Suggestion of 2 distinct types of CLL defined by the mutational status of the IgVH genes: 40-50% show no somatic mutations of their variable region genes (naïve B cells). 50-60% have somatic mutations consistent with derivation from post-germinal center B-cells.

• Cytogenetic abns and oncogenes:

– About 80% of the cases have abnormal karyotypes by FISH

– Trisomy 12 reported in 20% of cases, have predominantly unmutated Ig variable region genes

– Deletions at 13q14 in up to 50%, have mutations more often (Ig variable region genes)

– Deletions at 11q22-23 are found in 20% of cases. Somatic mutations have been found in the other allele in these cases

– Deletions at 6q21 or 17p13 (p53 locus) are seen in 5 and 10% of cases, respectively. p53 is expressed in 10% of cases

– t(11;14) and BCL1 gene rearrangement have been reported (may be leukemic MCL)

Postulated cell of origin

• Cells thought to correspond to recirculating CD5+ CD23+ IgM+ IgD+ naïve B cells, found in PB, primary follicle, and follicle mantle zone

• Also suggested to be an anergic, self-reactive CD5+ B-cell subset

• Cases that show V region mutations may correspond to a subset of peripheral blood CD5+ IgM+ B cells that appear to be memory B cells

Prognosis and predictive factors

• Clinical course is indolent, not considered to be curable with available therapy

• Purine nucleoside analogues, such as fludarabine, may result in sustained remissions

• Overall median survival is 7 years

• Clinical staging systems (Rai 0-IV and Binet A-C) are the best predictors of survival

• Cases of CLL/PL and diffuse BM involvement may have a worse prognosis

• Rapid doubling time (< 12 months) is a prediction of poor prognosis in stage A CLL

• Trisomy 12 correlates with atypical morphology and aggressive clinical course

• Abnormality of 13q14 are reported associated with long survival

• Mutations in Ig genes variable regions have a better prognosis than those with germline VH regions (median survival 7 yrs vs 3 yrs)

• CD38 expression appears to have worse prognosis

• 11q22-23 deletions have extensive lymphadenopathy and poor survival

• TP53 abnormality have also been reported to have a poor prognosis

• Transformation to high grade lymphoma (Richter syndrome) occurs in about. 3.5% of cases, usually DLBCL (3%), HL (0.5%), particularly in patients treated with purine nucleotide analogues.

• Molecular genetic analysis suggests about in 50% cases the aggressive lymphoma represents transformation of the original neoplastic clone. In the remainder the lymphoma maybe a second, unrelated neoplasm.

• Variant: Mu heavy chain disease

– Usually associated with neoplasm resembling CLL, in which a defective mu heavy chain lacking a variable region is produced

– BM has characteristic vacuolated plasma cells, admixed with small, round lymphocytes

– Patients are adults with hepato-splenomegaly, absence of peripheral lymphadenopathy, and a slowly progressive course

B-cell Prolymphocytic Leukemia

(B-PLL)

Definition

• Malignancy of B-prolymphocytes

– Round lymphoid cells

– Medium-sized

– Prominent nucleoli

• Affects PB, BM, and spleen

• Prolymphocytes: >55% of PB lymphoid cells

• Exclude

– Transformed CLL

– CLL with increased prolymphocytes

Epidemiology

• Extremely rare (~1% of lymphocytic leukemias)

• Elderly (most >60 y/o; median 70 y/o)

• Male predominance (M:F = 1.6:1)

Clinical features

• Most patients

– Marked splenomegaly

– No peripheral lymphadenopathy

– Rapidly rising lymphocyte count (usually >100 x 10⁹/L)

• 50% of patients

– Anemia

– Thrombocytopenia

• Some patients

– Serum M-component

Morphology in PB and BM

• PB Prolymphocytes

– >55% of circulating cells (usually >90%)

– Medium-sized (twice the size of a lymphocyte)

– Typically round nucleus (with or without indentation)

– Moderately condensed chromatin

– Prominent central nucleolus

– Small amount of faintly basophilic cytoplasm

• BM

– Diffuse intertrabecular infiltrate

Morphology in other tissues

• Spleen: extensive white and red pulp involvement, bizonal appearance of white pulp nodules (central “packed” cells; peripheral larger cells), morphology of prolymphocytes best seen in red pulp

• LN: diffuse or vaguely nodular infiltrates of prolymphocytes; no pseudofollicles

Immunophenotype

• Strongly positive for

– sIgM (+/- IgD)

• Positive for

– CD19/ CD20/ CD22/ CD79a/ CD79b

– FMC7

• CD5 positive in 1/3 of cases

• Negative for CD23

Genetics

• t(11;14)(q13;q32)

– In 20% of “typical” cases

– Some of these might be cases of leukemic presentation of blastoid variant of MCL

– Abnormalities of TP53 (p53 protein expression and mutations): 53% of cases (highest observed incidence in lymphoid malignancies)

• Deletions at 11q23 and 13q14 (by FISH)

Prognosis

• Poor response to CLL therapy

• Short survival

• May respond to

– CHOP (cytoxan, adriamycin, vincristine, and prednisone)

– Fludarabine (nucleoside analog)

– Cladribine (nucleoside analog)

– Splenic irradiation

• Splenectomy

– May improve patient’s general condition

– Does not delay disease progression

Lymphoplasmacytic Lymphoma (LPL) / Waldenstrom Macroglobulinemia (WM)

Definition

• Neoplasm of small B-lymphocytes, plasmacytoid lymphocytes, and plasma cells

• Usually involves: BM, LNs, and spleen

• Usually lacks CD5

• Has a serum monoclonal protein with hyperviscosity or cryoglobulinemia in most cases

• Plasmacytoid variants of other lymphomas must be excluded (B-CLL, MZL, FL)

Epidemiology

• Rare disease (1.5% of nodal lymphomas)

• Older adults (median age 63y/o)

• Slight male predominance (53%)

Sites of involvement

• Commonly involves BM, LNs, and spleen

• May involve: PB, extranodal sites with lung, GI, skin (most previously diagnosed cases are MZL of MALT-type)

Clinical features

• In most cases, monoclonal IgM paraprotein (>3g/dl in Waldenstrom macroglobulinemia)

• M-component may result in

– hyperviscosity (10-30% of patients) which causes: RBC sludging or rouleaux formation, reduced visual acuity, increased risk of CVA

– autoimmune reactions

– cryoglobulinemia

– neuropathies (10%)

• Paraprotein deposition in: skin, GI tract (causes diarrhea)

• Coagulopathy, due to binding of IgM to: clotting factors, platelets, fibrin

• Waldenstrom macroglobulinemia is NOT synonymous with LPL,

IgM paraprotein present in other diseases

– splenic MZL

– B-CLL

– Extranodal MZL of MALT type (rarely)

Etiology

• Hepatitis C virus

– In patients with HCV, cryoglobulinemia, and LPL, decreasing viral load with interferon is associated with regression of the lymphoma

– Mechanism is unclear:HCV has transforming potential, or LPL is antigen-driven

• Genetic susceptibility

• Occupational exposures

Morphology in LNs

• Growth pattern

– diffuse

– may be interfollicular with sparing of sinuses

• No pseudofollicles

• Neoplastic cells

– small lymphocytes

– plasmacytoid lymphocytes

– plasma cells , with or without Dutcher bodies

• Progression to diffuse large cell (immunoblastic) lymphoma may occur

Morphology in BM and PB

• BM: nodular and/or diffuse lymphoid infiltrate

• PB: if involved, WBC count typically is less than that in CLL

• Aspirate smears show a mixture of: small lymphocytes, plasmacytoid lymphocytes, and plasma cells

Immunophenotype

• sIg and cIg positive (usually IgM; sometimes IgG, rarely IgA)

• IgD negative

• CD19/ CD20/ CD22/ CD79a positive

• CD38 positive

• CD5/ CD10/ CD23 negative

• CD43 is variable

Genetics

• Antigen receptor genes

– Ig heavy and light chain genes are rearranged

– Variable-region genes show somatic mutations

• Cytogenetic abnormalities and oncogenes: t(9;14)(p13;q32): rearrangement of PAX-5 gene (encodes B-cell-specific activator protein; important in early B-cell development) and Ig heavy chain gene, in 50% patients (Not from WHO book: recent studies show that the more accurate percentage is about 5%, 6q del is more common in LPL)

Prognosis and predictive factors

• Indolent course

• Median survival of 5 years

• Asymptomatic patients: not treated

• Not curable with available treatment

• Poorer prognosis associated with: advanced age, PB cytopenias, neuropathies, weight loss, transformation to diffuse large B-cell lymphoma

Variant of Lymphoplasmacytic Lymphoma:

Gamma Heavy Chain Disease

• Results from secretion of a truncated gamma chain (lacks light-chain binding sites)

• Usually associated with a tumor resembling LPL, involving: LNs, BM, liver, spleen, PB

• Adults mostly

• Systemic symptoms due to autoimmune abnormality: hemolytic anemia, autoimmune thrombocytopenia

• Other systemic symptoms: arthritis, lymphadenopathy, splenomegaly, hepatomegaly, involvement of Waldeyer’s ring, peripheral eosinophilia

• Polymorphous proliferation of: lymphocytes, plasma cells, immunoblasts, eosinophils

• Variable clinical course (more aggressive than that of LPL)

Splenic Marginal Zone Lymphoma (SMZL)

Definition

· B-cell neoplasm

· Small lymphocytes that surround and replace the splenic white pulp germinal centers,
efface the follicle mantle and merge with a peripheral (marginal) zone of larger cells
including scattered transformed blasts

· Both small and larger cells infiltrate the red pulp

· Hilar lymph nodes and BM are often involved

· PB: villous lymphocytes may be seen

Epidemiology

· Rare, <1% of lymphoid neoplasms

· May account for most cases of otherwise unclassifiable chronic lymphoid leukemias that
are CD5-

· Most patients above 50 y/o, F=M

Site of Involvement and Clinical Features

· Splenomegaly

· Splenic hilar lymph nodes

· BM, usually positive

· PB villous lymphocytes, variable

· Liver in some cases

· Peripheral lymph nodes typically not involved

· Autoimmune thrombocytopenia or anemia, sometimes

· Extranodal infiltration, extremely uncommon

· Small monoclonal serum protein, 1/3 of cases. Marked hyperviscosity and hypergammaglobulinemia are uncommon.

Morphology-Spleen

· White pulp/central zone: small round lymphocytes, surround, or, more commonly replaces reactive germinal centers with effacement of the normal follicle mantle

· Peripheral zone of small to medium-sized lymphocytes with more dispersed chromatin and abundant pale cytoplasm resembling marginal zone cells and are interspersed with transformed blasts

· Red pulp: always infiltrated, small nodules of larger cells and sheets of the small lymphocytes, which often invade sinuses

· Epithelial histiocytes: may be present in the lymphoid aggregates

· Plasmacytic differentiation: may occur. Rarely, clusters of plasma cells may be present in the centers of the white pulp follicles.

Morphology-Hilar LN

· Sinuses are dilated

· Lymphoma surrounds and replaces germinal centers

· The two cell types (small lymphocytes and marginal zone cells) are often more intimately mixed without the formation of a distinct “marginal” zone

Morphology-BM

· Nodular interstitial infiltrate, cytologically similar to that in the lymph nodes

· Occasionally neoplastic cells surround reactive follicles

· Intrasinusoidal lymphoma cells are characteristic

Morphology-PB

· When present, usually show lymphocytes with short polar villi (villous lymphocytes)

· Some lymphocytes may appear plasmacytoid

Morphology-Differential Diagnosis

· Other small B-cell lymphoma/leukemias: CLL, HCL, MCL, FL, LPL

· Nodular pattern on BM excludes HCL, but BM morphology may not be sufficient to distinguish SMZL from others

· PB villous lymphocytes are helpful

· PB or BM flow cytometry results are helpful

· A diagnosis of exclusion in the absence of splenectomy

Immunophenotype

· Positive: sIgM, sIgD, CD20, CD79a

· Negative: CD5, CD10, CD23, CD43, cyclin D1, CD103

Genetics-Antigen Receptor Genes

· IgH and Ig light chain genes are rearranged

· Most cases have somatic mutation

· Intraclonal variation: ongoing mutations

Genetics-Cytogenetics

· Allelic loss of 7q21-32: 40% of cases, some of them with dysregulation of CDK6 gene

· No BCL2 rearrangement, ie. no t(14;18)

· No BCL1 rearrangement, ie. no t(11;14)

· Trisomy 3 and t(11;18), common in MALT, are uncommon in SMZL. Trisomy 3 reported in only 7 cases; no t(11;18) confirmed cases

Postulated cell of origin: post-germinal centre B cell of unknown differentiation stage

Prognosis and predictive factors

· Indolent clinical course, even with BM involvement

· Poor response to chemotherapy of the type that is typically effective in other chronic lymphoid leukemias, but typically have response to splenectomy with long term survival

· Transformation to large B-cell lymphoma may occur

Hairy Cell Leukemia

Definition:

· Neoplasm of small B lymphoid cells with oval nuclei and abundant
cytoplasm with hairy projections in bone marrow and peripheral blood,
diffusely infiltrating bone marrow and splenic red pulp

· Hairy cells positive for: CD11c, CD22, CD25, CD103, DBA-44

Typical features:

· 2% of lymphoid leukemias

· Middle aged to elderly adults (median age 55)

· M:F=5:1

· Splenomegaly

· Pancytopenia

· Monocytopenia

· Small to medium-sized cells

· Oval-indented nuclei

· Ground-glass chromatin (less condensed than that of normal lymphocytes)

· Nucleoli absent

· Abundant, pale cytoplasm with hairy projection

· BM: lymphocytes with fried-egg appearance; increased reticulin

· Spleen: red pulp disease (red blood cell lakes: pooled erythrocytes surrounded by elongated hairy cells), with white pulp atrophy

Immunophenotype:

· Positive: sIg (usually G), CD19, CD20, CD22, CD79a, CD11c, CD25, CD103, FMC7, TRAP, DBA-44

· Negative: CD5, CD10, CD23, CD79b

Genetics:

· Ig heavy and light chain genes are rearranged

· Cyclin D1 is overexpressed in 50-75% of cases with no association with t(11;14)

Postulated cell of origin: peripheral B cell of unknown post-germinal center stage

Prognosis: long term remission with interferon-alpha 2b, deoxycoformycin, or 2-chlorodeoxyadenosine (2CDA). Prolonged remission also follows splenectomy.

Hairy Cell Variants

· Leukocytosis (WBC 50k), absent monocytopenia

· Round-oval nuclei, more prominent nucleoli (resembling prolymphocyte)

· Immunophenotype: positive for sIgG, B cell markers, negative for CD25

· TRAP often negative

· Poor response to HCL therapy, significantly shorter survival

Plasma cell neoplasms

Introduction

•Plasma cell myeloma

•Plasmacytoma

•Monoclonal immunoglobulin deposition diseases

o Primary amyloidosis

o Monoclonal light and heavy chain deposition disease

o Osteosclerotic myeloma (POEMS syndrome)

o Heavy chain diseases

§ Gamma heavy chain disease

§ Mu heavy chain disease

§ Alpha heavy chain disease

• Immunosecretory disorders result from the expansion of a single clone of immunoglobulin secreting, terminally differentiated, end-stage B-cells

• These monoclonal proliferations of either plasma cells or plasmacytoid lymphocytes are characterized by secretion of a single homogeneous immunoglobulin product known as the M-component or monoclonal component

• The prominence of the M-component in serum and urine protein electrophoresis (SPE, UPE) has led to various designations for these disorders including monoclonal gammopathies, dysproteinemias and paraproteinemias

• The M-components, although monoclonal, may be seen in malignant conditions (plasma cell myeloma and Waldenström macroglobulinemia) and benign or premalignant disorders (MGUS)

• Variants of plasma cell myeloma include syndromes defined by the consequence of tissue immunoglobulin deposition, including primary amyloidosis (AL) and light and heavy chain deposition diseases

Plasma Cell Myeloma

• Bone marrow based, multifocal plasma cell neoplasm characterized by a serum monoclonal protein and skeletal destruction with osteolytic lesions, pathological fractures, bone pain, hypercalcemia, and anemia

• The diagnosis is based on a combination of pathological, radiological, and clinical features

Epidemiology

• In USA, plasma cell myeloma is the most common malignancy in Blacks and the second most common in Whites, representing 15% of all hematological malignancies

• From 1940 to the 1970´s the incidence of plasma cell myeloma has shown a net increase of 45%

• Median age is 68 in males and 70 in females. M:F ratio is 1:1

Sites of involvement

• Generalized BM involvement is typically present

• Lytic bone lesions and tumor masses of plasma cells also occur. The most common sites are in marrow areas of most active haematopoiesis, including in order of frequency, the vertebrae, ribs, skull, pelvis, femur, clavicle, and scapula.

Clinical features

• The extensive skeletal destruction results in bone pain, pathological fractures, hypercalcemia and anemia

• Recurrent bacterial infections and renal insufficiency are common

• The infections are in part a consequence of depressed normal Ig production due to displacement by the neoplastic clone

• Renal failure follows the tubular damage resulting from monoclonal light chain proteinuria

• Anemia is due both to marrow replacement and renal damage with resultant loss of erythropoietin

• An M-component is found in the serum or urine in 99% of the pts.

• The serum protein electrophoretic pattern shows a peak or localized band in 80% of patients

• Monoclonal IgG accounts for 50% and IgA for 20% of cases

• A monoclonal light chain (Bence-Jones protein) is found in the serum of 15% of patients, in the urine in 75% of patients

• IgD accounts for 2% while bi-clonal gammopathies are found in 1%

• The serum M-protein is usually >3g/dl of IgG and >2g/dl of IgA

Diagnostic criteria

•Major criteria

I. Plasmacytoma by biopsy

II. >30% marrow plasmacytosis

III. Monoclonal gammopathy

Serum: IgG>3.5 g/dl, or IgA>2 g/dl

Urine: >1 g/day of BJ proteins

•Minor criteria

A.10-30% marrow plasmacytosis

B. Monoclonal gammopathies with lower values than III above

C. Lytic bone lesions

D. Suppressed normal immunoglobulins

•To make diagnosis of myeloma: one major and one minor criteria or three minor criteria
which should include 1 and 2

•These criteria should be in symptomatic patients with progressive disease

Clinical variants

• Non-secretory myeloma:

o Rare cases (1%) of plasma cell myeloma have plasma cells that synthesize but do not secrete Ig molecules, leading to absence of M-component.

o Monoclonal cytoplasmic Ig is typically present in the neoplastic plasma cells when evaluated for immunophenotype.

o Clinical features are the same, except for a lower incidence of renal insufficiency.

· Smoldering and indolent myeloma: represent variants of plasma cell myeloma in which the diagnostic criteria for myeloma are met, but the patients are asymptomatic and the disease may be stable for long periods.

o Smoldering myeloma patients have higher levels of M-component and marrow plasmacytosis than patients with MGUS, and fulfill the minimal criteria for the diagnosis of plasma cell myeloma, but are asymptomatic and have no lytic bone lesions or other clinical features of myeloma including anemia, renal insufficiency, or hypercalcemia

o Indolent myeloma patients have up to 3 lytic lesions without bone pain, otherwise findings are similar to those with smoldering myeloma

Aetiology

• An increased risk (3-4 times) of myeloma has been described in cosmetologists, farmers, and laxative takers

• Specific exposure agents include pesticides, petroleum products, high dose radiation in survivors of the atomic bomb at Hiroshima and Nagasaki (myeloma rate 4.7 times greater than controls)

• Low level radiation exposure is implicated in increased incidence of myeloma among radiologists and nuclear plant workers

Precursor lesion: Monoclonal gammopathy of undetermined significance (MGUS)

• MGUS denotes the presence of an M-component in persons without evidence of plasma cell myeloma, WM, primary amyloidosis (AL), or other related disorders.

• Bone marrow plasma cells are less than 10%. Patients do not have lytic lesions.

• Approximately 25% patients with MGUS develop plasma cell myeloma, primary amyloidosis, macroglobulinemia, or other lymphoproliferative disease after follow-up for more than 20 years

Macroscopy: in plasma cell myeloma, the bone defects on gross examination are filled with a soft gelatinous, fish-flesh, hemorrhagic tissue.

Morphology: BM aspiration

· Myeloma plasma cells vary from mature to immature, pleomorphic or anaplastic forms

· The mature plasma cells are usually oval, with a round eccentric nucleus with “spoke wheel” or “clock-face” chromatin without nucleoli, with abundant basophilic cytoplasm and marked perinuclear hof

· Immature forms have dispersed nuclear chromatin, high N/C ratio, and prominent nucleoli (plasmablasts). About 10% patients have plasmablastic morphology associated with a poorer prognosis.

Immunophenotype

• Expresses monotypic cytoplasmic Ig and lacks surface Ig. The Ig is most commonly IgG, occasionally IgA, and rarely IgD, IgE, or IgM. In 85% of cases both heavy and light chains are produced; in 15% of cases light chain only (Bence-Jones myeloma).

• Most but not all lack CD19 and CD20

• CD38 and CD79a expressed in the majority of cases

• In contrast with normal plasma cells that express CD19 and lack CD56/58, myeloma cells lack CD19 and express CD56/58

• Collagen-1 binding proteoglycan syndecan-1 (CD138) is found in most cases of myeloma

• VS38c is typically expressed

• Occasional cases of myeloma express CD10

• The phenotype of plasma cell leukemia is comparable to that of myeloma, except for loss of some adhesion molecules (CD56), often express light chains only, IgE or IgD

Genetics

• Antigen receptor genes:

o While a single monoclonal rearranged Ig band is the rule in myeloma, multiple rearranged Ig bands are found in 5% of myeloma patients

o High frequency of Ig VH gene somatic mutation consistent with derivation from a post-germinal centre, antigen-driven B-cell

• Genetic abnormalities and oncogenes:

o Cytogenetic analysis in most cases is hampered by the low proliferation fraction

o Cytokine-stimulated BM cultures and in situ hybridization have increased the proportion of informative cases

o Structural and numerical chromosomal abnormalities are described in 20-60% of newly diagnosed patients, with a mean of 30-40% and in 60-70% of patients with progressive disease

o Complex karyotypes with multiple chromosomal gains and losses are the most frequent changes, but translocations, deletions and mutations are all reported

o Gains in chromosomes 3, 5, 7, 9, 11, 15, and 19, and losses in chromosomes. 8, 13, 14, and X are most common

o Among losses, monosomy or partial deletion of (13q14) is the most common finding, occurring in 15-40% of newly diagnosed cases

Postulated cell of origin: bone marrow-homing plasma cell

Prognosis and predictive factors

• Usually incurable, with a median survival of 3 years, and 10% survival at 10 years

• Using the myeloma staging scheme increased tumor burden and poor function are associated with shorter survival time

• Myeloma patients with normal renal function experienced a 37-month median survival versus 8 months for those with renal insufficiency

• Other prognostic factors include Hgb, Calcium, lytic bone lesions, and amount of the M-component beta-2-microglobulin (B2M)

• Estimation of the degree of marrow replacement by plasma cells in marrow core biopsies also has prognostic value. Three stages have been defined

• Stage I <20%

• Stage II 20-50%

• Stage III >50% plasma cells

Which predict progressively poorer prognosis

• Plasmablastic morphology is also associated with a poorer prognosis

• The proliferation antigen Ki-67 also identifies pats with a poor prognosis

• Genetic abns associated with a poorer prognosis include deletions of 13q14 and 17p13

Plasmacytoma

• Clonal proliferation of plasma cells (cytologically, morphologically, and immunophenotypically identical to myeloma cells) with localized growth pattern

• Localized growth pattern

o Osseous: solitary plasmacytoma of bone

o Extraosseous(extramedullary) plasmacytoma

Solitary Plasmacytoma of Bone

• Osseous plasmacytoma

• Localized bone tumor

• Solitary lytic lesion on X-rays

• No plasmacytosis in bone marrow away from lesion

• Epidemiology: rare (5% of plasma cell neoplasms)

• Sites of involvement: most commonly in marrow areas of most active hematopoiesis (vertebrae, ribs, skull, pelvis, femur, clavicle, scapula)

• Clinical features

o Presentation: bone pain, or pathological fracture

o No serum or urine M-protein (if present, it usually disappears after treatment)

• Morphology, immunophenotype, and genetics: identical to plasma cell myeloma

• Treatment: radiation therapy

• Prognosis at 10 years

o 55% develop plasma cell myeloma

o 35% cured

o 10% local recurrence or develop another solitary lesion at different sites

Extraosseous Plasmacytoma

• Extraosseous and extramedullary tumor

• Epidemiology

o 3-5% of plasma cell neoplasms

o Adults (median age 55)

o Males: Female=2:1

• Sites of involvement

o Upper respiratory tract (80%): oropharynx, nasopharynx, sinuses, larynx

o Other sites of involvement: GI tract, urinary bladder, central nervous system, breast, thyroid, testis, parotid gland, lymph nodes, skin

• Clinical features

o No evidence of plasma cell myeloma on bone marrow examination and by radiography

o May have monoclonal gammopathy (15-20%)

o No evidence of anemia, hypercalcemia, or renal insufficiency

• Morphology

o Similar to osseous plasmacytoma

o Some cases (particularly in GI) may represent MALT lymphoma with plasmacytic differentiation

• Differential diagnosis: reactive plasma cell infiltrates with polyclonal kappa and lambda light chain expression

• Immunophenotype and genetic features

o Not extensively studied

o Appear to be identical to those of plasma cell myeloma

• Treatment: radiation therapy

• Prognosis

o 25% of cases with regional recurrences

o 15% of cases develop plasma cell myeloma

Monoclonal Immunoglobulin Deposition Disease (MIDD)

· Visceral and soft tissue Ig deposition, resulting in compromised organ function

· Two major categories

o Primary amyloidosis: fibrillary protein with a beta-pleated sheet structure, which binds Congo red with apple-green birefringence, and contains amyloid-P component. Predominant lambda light chain.

o Monoclonal light chain and heavy chain deposition diseases: abnormal light chain or heavy chain (or both) that does not have a beta-pleated sheet configuration and does not bind to Congo red nor contain amyloid-P component. Predominantly kappa light chain.

· Primary amyloidosis:

o Rare disease in adults, 80% with monoclonal immunoglobulin, 20% having overt plasma cell myeloma

o 15% myeloma patients have or will develop primary amyloidosis

o Most frequently lambda light chain

o Sites of involvement

o Plasma cell-related amyloid (AL) accumulates in: heart (congestive heart failure), liver (hepatomegaly), kidneys (nephrotic syndrome and/or renal failure), gut (malabsorption), tongue (macroglossia), nerves (sensorimotor peripheral neuropathy and loss of sphincter control), bone, blood vessel (bleeding due to vessel fragility)

o Diagnostic sites: abdominal subcutaneous fat-pad, BM, or rectum

o Pathophysiology

o AL: primary or immunoglobulin-light chain (myeloma-associated) amyloidosis

o AA: secondary amyloidosis (inflammation-associated)

o AF: familial amyloidosis

o b2M: b-2 microglobulin amyloidosis (hemodialysis-associated)

o AL: intact immunoglobulin light chains secreted by monoclonal plasma cells, ingested, processed and discharged by macrophages into the extracellular matrix.

o Macroscopy: dense “porcelain-like” or waxy appearance.

o Microscopy:

§ H&E: amorphous, eosinophilic, waxy-appearing substance, with a characteristic cracking artifact, focally in thickened blood vessel walls, on basement membranes, and in the interstitium of tissues such as adipose tissue or bone marrow.

§ Congo red: pinkish red by standard light microscopy and “apple-green” birefringence by polarization microscopy.

o Immunophenotype: light chains: useful in distinguishing primary from secondary amyloidosis but background may be high in paraffin-embedded sections.

o Prognosis: patients with plasma cell myeloma and amyloidosis have a shorter survival period than those with myeloma alone.

Monoclonal light chain and heavy chain deposition diseases (LCDD and HCDD)

• Epidemiology
• Rare (<70 cases described)
• Age range: 33-79 years (56 year median)
• Usually associated with MGUS or myeloma
• No ethnicity effect and equal incidence in male and female
• Site of involvement: many organs, most commonly kidneys, liver, heart, nerves, blood vessels and occasionally joints. Prominent deposition of aberrant Ig on basement membranes, elastic and collagen fibers. Vascular occlusion and microaneurysm formation may occur
• Clinical Features

o Organ dysfunction: nephrotic syndrome, renal failure, arthritis, congestive heart failure, and coagulopathy due to liver involvement

o IgG3 or IgG1: hypocomplementemia

o Monoclonal gammopathy: 85% of cases

o No M-component: 15% of cases; representing strong tissue binding of the
aberrant Ig

• Pathophysiology
• Monoclonal Ig: structural changes due to deletion and mutation. Alteration in physiochemical properties or aberrant glycosylation, which favor tissue binding and deposition.
• HCDD
• CH1 deletion: secreted prematurely
• Substitutions in variable regions: increase in tissue deposition and binding blood elements
• LCDD
• Multiple mutations in light chain variable regions, with V_kIV over-represented, favoring tissue binding
• Most frequently kappa light chain (80% of cases)
• Morphology

o Monoclonal Ig deposit: non-amyloid, nonfibrillary, amorphous eosinophilic material, negative for Congo red

o Refractile eosinophilic material in glomerular and tubular basement membranes, but may also be seen in bone marrow and other tissues

o EM: discrete, dense punctate granular, nonfibrillary deposits

o X-ray diffraction: absence of the beta-pleated sheet structure

o Typically few plasma cells in the organs with Ig deposition; Ig produced in the BM and reach the site via circulation

o BM plasmacytosis: 50-60% cases

· Immunophenotype

o BM: aberrant kappa/lambda ratio, even without overt plasmacytosis

· Prognosis: very poor, fatal within 1-2 years even in the absence of aggressive plasma cell proliferation

Osteosclerotic Myeloma (POEMS Syndrome)

· Osteosclerotic myeloma often associated with
Polyneuropathy: sensorimotor demyelination
Organomegaly: liver, spleen
Endocrinopathy: diabetes mellitus, gynecomastia, testicular atrophy, impotence
Monoclonal gammopathy
Skin changes: hyperpigmentation

· Other associations: Castleman disease (angiofollicular hyperplasia)

· 1-2% of plasma cell dyscrasias

· Adults (median age 50 years)

· Male-to-female ratio 1.4:1

· Some association with Kaposi sarcoma and Herpes Virus 8 (HHV 8)

· Monoclonal cIg (IgG or IgA heavy chain type), light chain lambda in >90%

· Prognosis: survival 60% at 5 years (better than that for multiple myeloma)

Gamma Heavy Chain Disease

· A lymphoplamacytic neoplasm that produces a truncated gamma chain, which lacks light-chain binding sites and does not bind to light chains to form a complete immunoglobin molecule

· Sites of involvement: lymph nodes, Waldeyer’s ring, bone marrow, liver, spleen,
peripheral blood

· Epidemiology: rare, median age: 60

· Clinical features

o Associated with lymphoplasmacytic lymphoma

o No lytic bone lesions

o SPE: normal-looking or sometimes broad band (infection-like)

o Immunofixation: IgG (truncated) without light chains

o Urine protein: <1g/24h

o Median survival 12 months

Mu Heavy Chain Disease

o Extremely rare, associated with B-cell neoplasm resembling CLL, with truncated mu heavy chain, slowly progressive

o Involves: spleen, liver, bone marrow, peripheral blood. Lymph nodes are usually spared

o Routine SPE: frequently negative

o Immunofixation: Mu fragments in diverse sizes

o Urine Bence-Jones light chains: in 50% of cases, mostly kappa (cannot bind to Mu chains)

o Monoclonal cytoplasmic Mu heavy chains without light chains

o Pan B-cell Antigens (+), CD5(-), CD10 (-)

o Bone marrow: vacuolated plasma cells with small lymphocytes

o Prognosis: slowly progressive

Alpha Heavy Chain Disease

o A variant of MALT (immunoproliferative small intestinal disease or IPSID), in which a defective alpha heavy chain is secreted

o Involves GI tract in young adults resulting in diarrhea, malabsorption

o May respond to antibiotics but may also lead to high grade lymphoma

o Peak incidence in second and third decades

o Common in areas bordering Mediterranean

o Plasma cells and marginal zone cells: monoclonal cytoplasmic alpha heavy chains without light chains

o Pan B-cell Antigens (+), CD5 (-), CD10 (-)

• Early phase, may completely remit with antibiotic therapy
• However, many transform to DLBCL, and frequently fatal

Marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue

(MALT lymphoma)

• Definition: an extranodal lymphoma comprising morphologically heterogeneous small B-cells including marginal zone (centrocyte-like) cells, cells resembling monocytoid cells, small lymphocytes, and scattered immunoblast and centroblast-like cells. There is plasma cell differentiation in a proportion of the cases.

• The infiltrate is in the marginal zone of reactive B-cell follicles and extends into the interfollicular region. In epithelial tissues, the neoplastic cells typically infiltrate the epithelium, forming lymphoepithelial lesions.

• Epidemiology: MALT lymphoma comprises 7-8% of all B-cell lymphomas and up to 50% of primary gastric lymphoma.

• Most cases occur in adults with a median age of 61 and a slight female preponderance (M:F ratio 1:1.2). There appears to be a higher incidence of gastric MALT lymphomas in north-east Italy and a special subtype called immunoproliferative small intestinal disease (IPSID) occurs in the Middle East and the Cape region of South Africa.

• Precursor lesions and conditions: in many cases of MALT lymphoma, there is a history of chronic inflammatory, often autoimmune disorders that result in accumulation of extranodal lymphoid tissue. Examples: H. pylori associated chronic gastritis, Sjögren syndrome or Hashimoto thyroiditis.

• Sites of involvement: the gastrointestinal (GI) tract is the most common site of MALT lymphoma, comprising 50% of all cases, the stomach is the most common location (85%). The small intestine and colon are typically involved in IPSID. Other common sites include lung (14%), head & neck (14%), ocular adnexae (12%), skin (11%), thyroid (4%), and breast (4%).

• Clinical features: the majority of pts present with stage I or II disease. Aprox. 20% of patients have bone marrow involvement, but the frequency seems to vary among primary sites, being lower for gastric cases and higher for primary ocular adnexal or pulmonary cases. Multiple extranodal sites may be involved in up to 10% of the cases at the time of presentation.

• Despite plasmacytic differentiation in many of the cases, a serum paraprotein (M-component) is rare in MALT lymphomas. The major exception is IPSID, in which an aberrant alpha heavy chain can usually be found in the peripheral blood.

• The term “high-grade MALT lymphoma” should not be used, and the term “MALT lymphoma” should not be applied to a large B-cell lymphoma even if it has arisen in a MALT site.

• Differential diagnosis: distinction from reactive processes is based mainly on the presence of destructive infiltrates of extrafollicular B cells, typically with the morphology of marginal zone cells. In borderline cases, immunophenotyping or molecular genetic analysis to assess B-cell clonality are necessary to establish or exclude a diagnosis of MALT lymphoma. Distinction from other small B-cell lymphomas is based on a combination of the characteristic morphologic and immunophenotypic features.

• Immunophenotype: tumour cells typically express IgM, and less often IgA or IgG, and show light chain restriction. The tumour cells are CD20+, CD79a+, CD5-, CD10-, CD23-, CD43+/-, CD11c+/-(weak).

• In IPSID, both the plasma cells and marginal zone cells express alpha heavy chain without any light chain

• There is no specific marker for MALT lymphoma at present.

• Genetic abnormalities and oncogenes:

o Trisomy 3 is found in 60% and t(11;18)(q21;q21) has been observed in 25-50% of the cases.

o In contrast, t(11;18) is not found in primary large B cell gastric lymphoma. Recently, analysis of the t(11;18) breakpoint has shown fusion of the apoptosis-inhibitor gene API2 to a novel gene at 18q21, named MLT.

• Postulated cell of origin: post germinal centre, marginal zone B-cell.

• Prognosis: MALT lymphomas run an indolent natural course and are slow to disseminate. Recurrences may involve other extranodal sites. The tumours are sensitive to radiation therapy, and local treatment may be followed by prolonged disease-free intervals. Involvement of multiple extranodal sites and even bone marrow involvement do not appear to confer a worse prognosis.

• Protracted remissions may be induced in H. pylori-associated gastric MALT lymphoma by antibiotic therapy for H. pylori. Cases with the t(11;18)(q21;q21) appear to be resistant to H. pylori eradication therapy.

• In IPSID, remissions have followed therapy with broad spectrum antibiotics.

• Transformation to diffuse large B-cell lymphoma may occur.

Nodal Marginal Zone B-cell lymphoma

• Definition: NMZL is a primary nodal B-cell neoplasm that morphologically resembles lymph nodes involved by marginal zone lymphomas of extranodal or splenic types, but without evidence of extranodal or splenic disease. Monocytoid B-cells may be prominent.

• Epidemiology: nodal marginal zone lymphoma is a rare disease, comprising only 1.8% of lymphoid neoplasms

• Sites of involvement: peripheral lymph nodes, occasionally bone marrow and peripheral blood

• Clinical features: most patients present with localized or generalized peripheral lymphadenopathy, with good performance status

• Morphology: the marginal zone and interfollicular areas of the lymph node are infiltrated by marginal zone (centrocyte-like) B-cells, monocytoid B-cells, or small B lymphocytes, with scattered centroblast- and immunoblast-like cells.

• Two types described:

o One that closely resembles nodal involvement by MALT lymphoma

o One that resembles splenic marginal zone lymphoma

• Plasma cell differentiation is a feature of some cases

• Follicular colonization may be present

• Transformation to large B-cell lymphoma may occur

• In patients with extranodal (MALT) lymphoma, Hashimoto thyroiditis or Sjögren Syndrome, nodal involvement by marginal zone lymphoma should be considered secondary involvement by MALT lymphoma.

• Immunophenotype: similar to MALT lymphoma. Some are reported to be IgD+, CD43-, similar to splenic MZL.

• Genetics: not well studied. However, t(11;18)(q21;q21) and trisomy 3 associated with extranodal marginal zone lymphoma are not frequent.

• Postulated cell of origin: marginal zone B-cell of nodal type

• Prognosis: the clinical course has not been well studied. In two recent series, the majority of the patients responded to chemotherapy, but with a high early relapse rate; nonetheless, the median survival was approximately 5 years, consistent with an indolent lymphoma.

Follicular Lymphoma

Definition:

· Neoplasm of follicular centre B cells, with at least a partially follicular pattern. The lymphoma cells consist of two types: centrocytes (cleaved follicle centre B cells), and centroblasts (non-cleaved follicle centre B cells)

· Predominantly adults, median age 59 yrs; male to female ratio of 1:1.7

· 70% of low grade lymphomas

· Most patients have widespread disease at diagnosis (bone marrow involvement in 40-50%)

· Patients are usually asymptomatic at diagnosis, except for lymph node enlargement

Morphology:

· Follicular architecture

· Neoplastic follicles are: poorly defined and closely packed, no mantle zone, no polarization, no tingible body macrophages

Pattern:

· Follicular > 75% follicular

· Follicular and diffuse 25-75% follicular

· Minimally follicular < 25% follicular

Grading:

· Grade 1: 0-5 centroblasts / hpf

· Grade 2: 6-15 centroblasts / hpf

· Grade 3: > 15 centroblasts / hpf

o 3a: Some centrocytes present

o 3b: Solid sheets of centroblasts

Immunophenotype:

· Surface Ig +

· Express B-cell antigens: CD 19, CD 20, CD 22, CD 79a

· CD 10 +

· BCL 2 + (can help distinguishing from reactive follicles; however, grade 3 and cutaneous type may be negative)

· BCL 6 +

Genetics:

· t(14;18) (q32;q21)

• BCL 2 rearrangement, present is 70-95% cases
• Confers a survival advantage on B cells; failure to switch off BCL 2 during blast transformation may contribute to development of lymphoma by preventing apoptosis

Prognosis:

· Grades 1 and 2: indolent

· Grade 3: aggressive; treatment as for DLBCL

· 25-33% cases progress to DLBCL

Variants:

(1) Diffuse Follicle Centre Lymphoma:

• Centrocytes and centroblasts (minority) but no follicles
• Both cell types must have follicle centre cell phenotype (SIg+, CD 10+, BCL2+, BCL6+)
• If centroblasts predominate, or if the small cells are T cells, DLBCL is the diagnosis

(2) Cutaneous Follicle Centre Lymphoma:

• Partially follicular pattern
• Composed of cells that resemble centrocytes (often large) and centroblasts
• Often BCL2 –
• Occur on head and trunk, tend to remain localized to the skin; amenable to local therapy

Mantle Cell Lymphoma

Definition

· B-cell neoplasm of monomorphous small to medium-sized cells that resemble
centrocytes

· Median age: 60 yrs

· Male predominance (at least about 2:1)

· Extranodal sites: bone marrow (50-60%), GI (30%, multiple lymphomatous polyposis in large intestine), and Waldeyer’s ring

· Most patients present with lymphadenopathy, hepatosplenomegaly

Morphology

· Monomorphic proliferation of small to medium-sized lymphoid cells that resemble centrocytes

· Vague nodular/ diffuse / mantle zone growth pattern

· Hyalinized small blood vessels

Immunuphenotype

· Intense sIg (IgM +/- IgD)

· CD5 +, CD43 +, BCL-2 +, Cyclin D1 +

· Cyclin D1 seen in 70-80% of cases

· CD10 -, BCL-6 –

Genetics

· t(11;14) (q13;q32): chr 11 Cyclin D1, chr14 Ig heavy chain

Blastoid Variant

· Cells resemble lymphoblasts with dispersed chromatin

· High mitotic rate (>10/10 hpf)

Prognosis

· Median survival 3-5 yrs

· Vast majority cannot be cured

Diffuse Large B Cell Lymphoma

Definition

· Diffuse proliferation of large neoplastic B lymphoid cells

· Nuclear size equal to or exceeding normal macrophage nuclei or more than twice the size of a normal lymphocyte

Epidemiology

· 30-40% of adult non-Hodgkin lymphomas in western countries; higher proportion in developing countries

· Broad age range (median: 7th decade) including children

· Slightly more common in males

· Increasing incidence, independent of HIV

Site of Involvement

· Nodal or extra-nodal

· Up to 40% are at least initially confined to extranodal sites

· Most common extranodal site: GI (stomach or ileo-coecal region)

· Virtually any extranodal location

· Primary tumor in BM and/or PB is rare

Clinical Features

· A rapidly enlarging, often symptomatic mass at a single nodal or extranodal site

· With staging evaluation, many patients have disseminated disease

Etiology

· Unknown

· Usually de novo but can represent progression / transformation of a less aggressive lymphoma

· Immunodeficiency is a significant risk factor

· DLBCL in the setting of immunodeficiency are more often EBV-positive than sporadic DLBCL

Macroscopy

· Homogeneous fish-flesh replacement of most if not all of the structure

· The appearance of the lesion can be modified by hemorrhage or necrosis

· In extranodal sites, usually form a tumor mass with or without fibrosis

Morphology

· Typically replaces the normal architecture in a diffuse pattern

· LN involvement may be complete, partial, interfollicular, or, less commonly sinusoidal

· The perinodal soft tissue is often infiltrated; broad or fine bands of sclerosis may be observed

· Composed of large transformed lymphoid cells. Cytologically, they are diverse and can be divided into morphologic variants

· Distinction among these variants has generally met with poor intraobserver and interobserver reproducibility

· Immunophenotypic and genotypic parameters have not helped to delineate distinctive morphologic subtypes, with rare exceptions

· Pathologists have the choice to use only the term DLBCL or to use one of the specific morphologic variants

· Most cases will conform to one of the morphologic variants, with centroblastic being the most common

Morphologic Variants

· Centroblastic

o Medium to large cells with oval to round, vesicular nuclei with fine chromatin and 2-4 nucleoli. The cytoplasm is generally scanty and amphophilic to basophilic

o May have a monomorphic or polymorphic appearance. Cells may be multilobated. Centroblast-like cells may be admixed with multilobated cells and up to 90% immunoblasts

Immunoblastic

o Immunoblasts > 90%, with a single centrally located nucleolus and an appreciable amount of basophilic cytoplasm

o Centroblasts <10%

o Plasmacytoid differentiation may be present

o Clinical and/or immunophenotypic findings may be essential in differentiating from extra-medullary involvement by a plasmablastic variant of plasma cell myeloma

T-Cell / Histiocyte Rich

o Majority of cells are T-cells with or without histiocytes; <10% large neoplastic B-cells

o Histiocytes may or may not be epithelioid. The large cells may resemble L&H cells, centroblasts, immunoblasts, or Reed-Sternberg cells

o B-cells are rare to infrequent. Increased B-cells: possibility of NLPHL (especially vaguely nodular growth pattern)

o Immunophenotypic studies may be essential in the differential diagnosis with classical HL. Many diffuse mixed lymphoma cases in the working formulation represent the this variant of DLBCL

Anaplastic

o Very large round, oval, or polygonal cells with bizarre pleomorphic nuclei which may resemble RS cells

o The cells may grow in a cohesive pattern mimicking carcinoma and may show a sinusoidal pattern of growth

o These cases are biologically and clinically unrelated to ALCL of cytotoxic T-cell derivation

Immunophenotype

• Express pan-B markers (CD19, CD20, CD22, and CD79a), but may lack one or more
• Surface/cyto Ig (lgM> IgG>lgA): 50-75%. Cyto Ig is often seen in cases with plasmacytic differentiation
• CD30: vast majority of anaplastic LBCL and occasional non-anaplastic cases
• CD5+ in 10% and CD10+ 25-50%. CD5+ DLBCL are negative for cyclin D1 (vs blastoid MCL). CD5+ DLBCL may arise de novo rather than as progression of SLL/CLL
• BCL2+ in 30-50%
• BCL6+ in a very high proportion of cases
• P53 expression, usually associated with TP53 mutations, in a minority of cases
• Plasma cell-associated markers such as syndecan (CD 138) in a minority of cases
• Ki-67+ is usually high (>40%) and may be greater than 90%

Genetics

• Most cases have rearranged Ig H and L chain genes and show somatic mutations in the variable regions
• t(14:18) occurs in 20-30%
• Up to 30% show abnormalities of the 3q27 involving BCL6
• MYC rearrangement is uncommon
• Many cases exhibit complex cytogenetic abnormalities
• EBV+ is more common in cases associated with immunodeficiency
• DNA microarrays identified two major molecular categories with gene expression patterns suggestive of different stages of B-cell development. One type had an expression profile characteristic of germinal center B-cells, whereas the other type had a profile similar to that of in vitro activated peripheral blood B-cells

Postulated Cell of Origin

· Peripheral B-cells of either germinal center or post germinal center origin

Prognosis and Predictive Factors

· Aggressive but potentially curable

· Adverse prognostic indicators: high proliferative rate, BCL2 and P53 overexpression

· Better prognosis indicator: BCL6 translocation

Other Rare Variants/Subtypes with Distinct Immunophenotypic Features

Plasmablastic

· Typically presents in the oral cavity in the setting of HIV infection

· EBV+ in 60% of cases

· Although these lymphomas are indistinguishable from some immunoblastic lymphoma on morphologic grounds, few if any of the lymphoma cells stain for CD20 and CD45 but they do express plasma cell markers such as vs38c and CD138

· High growth fraction, absence of mature monoclonal plasma cells, and the characteristic clinical features help to distinguish this variant from plasma cell myeloma

DLBCL with expression of full-length ALK

· Composed of monomorphic large immunoblast-like cells, with round pale nuclei containing large central nucleoli and an abundant amphophilic cytoplasm (basophilic with the Giemsa stain) with sometimes plasmablastic differentiation. Some Reed-Sternberg-like cells are often seen. Lymph nodes are massively infiltrated with invasion of the sinuses.

· CD30- but express CD45 (weakly), EMA (strongly), and VS38 (ER-associated marker). Cyto IgA+ with light chain restriction. Lack other B or T markers with the exception of CD4 and CD57.

· Anti-ALK shows a granular cytoplasmic and dot-like positivity in the Golgi area, no finding of t(2;5). The mechanism of ALK upregulation is unknown. More frequently in adults and in males. Aggressive course.

Mediastinal (thymic) Large B-cell Lymphoma

• Subtype of DLBCL which arises in the mediastinum of putative thymic B-cell origin with distinctive clinical, immunophenotypic and genotypic features

• Epidemiology: most patients in their third to fifth decade

• Female predominance

• Clinical features: patients present with localized disease

• With signs and symptoms relating to anterior mediastinal masses, superior vena cava syndrome

• Disseminated disease: other extranodal sites such as kidney, adrenal, liver, skin and brain

• Etiologies: no epidemiologic clustering or evidence of specific risk factors have been identified. EBV is not present

• Morphology: diffuse proliferation with variably dense compartmentalizing fibrosis

• Identification of thymic remnants may be facilitated by IHC (keratin). These remnants may organize in clusters mimicking carcinoma

• Neoplastic cells vary in size, nuclear shape, most cases, cells have abundant cytoplasm

• Small numbers of interspersed benign lymphocytes and eosinophils may raise the suspicion of HL

• Mediastinal localization tissue biopsy may be obscured by fibrosis and cellular “crush” artifact

• Immunophenotype: B-cell immunophenotype: express CD19 and CD20

• Both immunoglobulin and HLA class I and II molecules are incompletely expressed or absent

• CD10 and CD5 are also absent

• CD30 expression is weak, tumor cells express CD45 (LCA)

• Genetics: immunoglobulin gene rearrangements are demonstrable

• Gains in chromosome 9p and amplification of the REL gene

• Overexpression of MAL has been identified

• Postulated cell of origin: thymic B cell

• Prognosis: response to chemotherapy with or without radiotherapy is usually good

• Patients with disease extending into adjacent thoracic viscera have poorer prognosis than patients with disease confined to the mediastinum

Intravascular large B-cell Lymphoma

• Definition: rare subtype of extranodal DLBCL characterized by the presence of lymphoma cells only in the lumina of small vessels, particularly capillaries

• Epidemiology: adults. Based on the small number of cases reported in the literature, no distinctive epidemiological features can be identified

• Sites of involvement: this lymphoma is usually widely disseminated in extranodal sites at presentation (CNS, skin, lung, kidneys, adrenals)

• Intravascular involvement may also be seen in the marrow

• Clinical features: symptoms are highly variable since most result from occlusion of small vessels by tumour cells in a variety of organs

• It most commonly presents with skin lesions (skin plaques and nodules) or neurological symptoms (dementia, focal symptoms)

• About 9% of patients present with B symptoms

• Multiple organs may be involved and a variety of clinical presentations have been described. These include nephrotic syndrome, pyrexia and hypertension, breathlessness and hematological abnormalities (autoimmune hemolytic anemia, leukopenia, pancytopenia and disseminated intravascular coagulation)

• Pathophysiology: the intravascular growth pattern has been hypothesized to be secondary to a defect in homing receptors of the neoplastic cells.

• Rare cases have cells with anaplastic features

• In organs such as the lung and bone marrow, the involvement may be very subtle. The recognition of single neoplastic cells may be enhanced by immunostains for CD45 and CD20

• Malignant cells are rarely seen in cerebrospinal fluid and blood

• Immunophenotype: tumor cells are usually positive for B-cell associated antigens (e.g. CD19, CD20, CD22, CD79a). CD5 coexpression is seen in some cases.

• Rare cases of intravascular lymphoma of T-cell phenotype have been reported

• Factor VIII may be detected, but is considered to represent absorption of factor VIII, rather than expression by the neoplastic cells

• Genetics: the majority of cases studied have had immunoglobulin gene rearrangements

• Karyotypic abnormalities have been described, but few cases have been studied for any consistent patterns to emerge

• Postulated cell of origin: transformed peripheral B-cell

• Prognosis: in general this is an extremely aggressive lymphoma which responds poorly to chemotherapy. Death occurs in most cases within a short time of presentation. The poor prognosis reflects in part frequent delays in diagnosis due to their protean presentation

• There is some evidence for a variant confined to skin which may have a relatively better prognosis but numbers of patients studied are small

Primary Effusion Lymphoma

• Primary effusion lymphoma (PEL) is a neoplasm of large B-cells usually presenting as serous effusions without detectable tumor masses

• It is universally associated with human herpes virus 8 (HHV-8)/Kaposi sarcoma herpes virus (KSHV), most often occurring in the setting of immunodeficiency

• Epidemiology: the majority of cases arise in the setting of HIV infection

• Most patients are young to middle aged homosexual males

• This neoplasm is rare even in the setting of HIV infection. At least one case has been reported in an HIV negative allograft recipient

• The disease also occurs in the absence of immunodeficiency especially in elderly males most often from areas with high prevalence for HHV-8/KSHV infection such as the Mediterranean.

• Sites of involvement: the most common sites of involvement are the pleural, pericardial and peritoneal cavities

• Typically only one body cavity is involved

• Other sites of involvement include the gastrointestinal tract, soft tissue and other extranodal sites

• Clinical features: patients typically present with effusions in the absence of lymphadenopathy or organomegaly

• Some patients have preexistent Kaposi sarcoma

• Rare cases may be associated with multicentric Castleman disease

• Etiology: the neoplastic cells are positive for HHV-8/KSHV in all cases

• Most cases are coinfected with EBV.

• Pleural biopsies show tumour cells adherent to the pleural surface often embedded in fibrin and occasionally invading the pleura

• This disease should be distinguished from pyothorax associated DLBCL which usually presents with a pleural mass lesion. The cells of that tumour are EBV positive and HHV8/KSHV negative

• Immunophenotype: lymphoma cells usually express leukocyte common antigen (CD45) but are usually negative for pan-B-cell markers such as CD19, CD20 and CD79a

• Surface and cytoplasmic expression of immunoglobulin is likewise often absent

• Activation and plasma cell-related markers such as CD30, CD38, and CD138 are usually demonstrable

• Aberrant cytoplasmic CD3 expression has been reported

• Because of the markedly aberrant phenotype, it is often difficult to assign a lineage with immunophenotyping.

• The nuclei of the neoplastic cells are positive by immunohistochemistry for the HHV-8/KSHV-associated latent protein. This is very useful in establishing the diagnosis

• Despite the usual presence of EBV, staining for LMP-1 is negative

• Genetics: immunoglobulin genes are rearranged and are mutated

• No characteristic chromosomal abnormalities have been identified

• HHV-8/KSHV viral genomes are present in all cases

• EBV is found in most cases and is most reliably detected by EBER in situ hybridization. EBV tends to be absent in elderly HIV-negative patients.

• Postulated cell of origin: post-germinal centre B-cell

• Prognosis: the clinical outlook is extremely unfavorable, with or without therapy

• Median survival is less than six months

Burkitt Lymphoma

• Definition:

o Highly aggressive lymphoma often presenting at extranodal sites or as an acute leukemia

o Composed of monomorphic medium-sized B-cells with basophilic cytoplasm and numerous mitotic figures

o Translocation involving MYC is a constant genetic feature

o EBV is found in a variable proportion of cases

• Epidemiology: three clinical variants are recognized. Each manifesting differences in clinical presentation, morphology and biology

Endemic BL:

o This variant occurs in equatorial Africa and Papua, New Guinea

o representing the most common malignancy of childhood

o Peak incidence at 4 to 7 years

o Male to female ratio of 2 to 1

Sporadic BL:

o Seen throughout the world, mainly in children and young adults

o The incidence is low, 1-2% of all lymphomas in Western Europe and in USA

o Accounts for approx. 30 to 50% of childhood lymphomas

o Median age in adult pts is 30 years

o Male to female ratio is about 3 to 1

o Low socio-economic status and early EBV infection are associated with higher
prevalence of EBV positive BL

Immunodeficiency associated BL:

o Seen primarily associated with HIV infection

o EBV is identified in 25-40% of the cases

o BL is less often seen in other immunodeficiency states

• Sites of involvement: extranodal sites are most often involved

o In all three variants pts are at risk for CNS involvement

o In endemic BL, the jaws and other facial bones are the site of presentation in about
50% of the cases

o In sporadic BL, the majority of cases present with abdominal masses

o In immunodeficiency-associated BL, nodal and bone marrow involvement are common

• Clinical features: pts present with bulky disease

• The clinical presentation varies according to the epidemiologic subtype and the site of involvement. Some present as acute leukemia with PB and BM involvement. BM involvement is a poor prognostic sign and is often found in pts with high tumor burden. Pts with bulky tumors or leukemia, high uric acid and high LDH are usually seen

• Localized stages (I and II) are found in approx. 30% of the cases

• Advanced stages (III and IV) are seen in about 70% of cases at presentation

• The tumor lysis syndrome is often seen with therapy and is characteristic of BL

• Etiology: EBV plays an important role in endemic BL

• In endemic BL, the EBV genome is present in the majority of neoplastic cells in all pts

• The lymphoma is preceded by a long period of polyclonal B-cell activation due to multiple bacterial, viral (EBV, HIV) and parasitic infection

• In sporadic BL, the frequency of EBV association is low, less than 30% of the cases

• Low socio-economic status and early EBV are associated with higher prevalence of EBV-BL

• In immunodeficiency-associated cases, EBV is identified only in 25 to 40% of the cases

• In cases of EBV negative BL, it is hypothesized that the virus may not be essential in the pathogenesis, but rather represent only a co-factor

• Genetic abnormalities involving the MYC gene at chromosome 8q24 play a essential role in the pathogenesis

• Macroscopy: Involved organs are replaced by masses of fish-appearing tissue, often associated with hemorrhage and necrosis. Adjacent organs are compressed/or infiltrated

• Nodal involvement is rare in endemic and sporadic BL

• Morphology: classical BL observed in endemic and sporadic cases

o Medium-sized cells show a diffuse monotonous pattern of infiltration

o Sometimes after fixation the cells exhibit squared off borders of retracted cytoplasm and may appear cohesive

o The nuclei is round with clumped chromatin and relatively clear parachromatin

o The nuclei contain multiple basophilic medium-sized, centrally located nucleoli

• The cytoplasm is deeply basophilic and usually contains lipid vacuoles

• The tumor has an extremely high proliferation rate (many mitotic figures)

• High rate of spontaneous cell death

• A “starry sky” pattern is usually present

• The nuclei of the tumor cells approximate in size those of the admixed starry-sky histiocytes

• Variants

BL with plasmacytoid differentiation

o Eccentric basophilic cytoplasm

o Single central nucleolus

o Monotypic intra-cytoplasmic Ig can be demostrated

o Certain degree of pleomorphism in nuclear size and shape can be recognized

o This variant can be observed in children, but is more common in immunodeficiency states

Atypical Burkitt/Burkitt-like

o Composed of medium-sized Burkitt cells and shows other features of BL

o The diagnosis requires a growth fraction of 100%

o This variant shows greater pleomorphism in nuclear size and shape

o Nucleoli are more prominent

o Nucleoli are larger and fewer in numbers

o The term a “atypical Burkitt/Burkitt-like” is reserved for cases with proven or strong presumptive evidence of MYC translocation

• Immunophenotype: tumor cells express IgM with light chain restriction and B-cell associated antigens (CD19, CD20, CD22, CD10 and BCL6)

• Negative for CD5, CD23 and TdT

• BCL2 is not expressed

• The expression of CD10 and BCL6 point towards follicle center origin

• CD21 can be expressed in the endemic form

• Monotypic cytoplasmic Ig can be demonstrated in the plasmacytoid variant

• A high growth fraction is observed: nearly 100% of tumor cells are positive for Ki-67

• Blasts of BL presenting with leukemia have a mature B-cell phenotype

• Genetics: clonal rearrangements of the Ig heavy and light chains genes

• Somatic mutations of the Ig genes are found

• All cases have the translocation of MYC at band q24 from chromosome 8 to the Ig heavy chain region on chromosome 14 [t(8;14)] at band q32

• Less commonly to a light chain loci on 2q11 [t(2;8)] or 22q11 [t(8;22)]

• Other genetic lesions include inactivation of TP53 in up to 30% of sporadic and endemic cases

• The MYC translocation is not specific for BL. The MYC translocation has been reported in secondary precursor B-lymphoblastic leukemia/lymphoma following follicular lymphoma

• Postulated cell of origin: germinal centre B-cell

• Prognosis: in endemic and sporadic cases the tumor is very aggressive but potentially curable

• Treatment should begin as early possible

• Intensive chemotherapy combination regimens result in cure rates up to 90% in pts with low stage disease and 60-80% in pts with advanced disease

• The results are better in children than in adults

• Pts with advanced stage disease, including BM and CNS involvement may be cured with high dose tx

• Relapse, when occur is usually during the first year after dx

• Pts without relapse for 2 years can be regarded as cured

• In Burkitt leukemia, the tx consists of very intensive chemotherapy of relatively short duration and with such a tx most pts have a very good prognosis with 80-90% survival

Lymphomatoid Granulomatosis

• Described by Liebow in 1972

• Lymphoproliferative disease

• Angiocentric and angiodestructive

• Extranodal sites

• EBV-positive B-cells

• Reactive T-cells (predominant cells)

• Lymph nodes usually spared

• Spectrum of histological grade

• Spectrum of clinical aggressiveness (related to the proportion of large B-cells)

• May progress to an EBV-positive DLBCL

• Must be distinguished from NK/T-cell lymphoma, nasal-type

• Epidemiology: rare

• Adults, usually

• Children with immunodeficiency disorders

• M:F > 2:1

• Sites of involvement: lung most common site (most patients have pulmonary involvement), skin (25-50%) second most common site, kidney (32%), liver (29%), brain (26%), upper respiratory tract, GI tract. LN and spleen are rarely involved.

• Clinical features: patients frequently present with respiratory tract signs and symptoms

o Cough (58%)

o Dyspnea (29%)

o Chest pain (13%)

• Common constitutional symptoms

Fever, malaise, weight loss, neurologic symptoms, arthralgias, myalgias, GI symptoms

• Very few patients (<5%) are asymptomatic

• Patients presenting without apparent immunodeficiency symptoms usually are found to have reduced immune function after careful clinical and laboratory analysis

• Etiology: EBV-driven disease. Underlying immunodeficiency increases risk

• Predisposing conditions

o Allogeneic organ transplantation

o Wiskott-Aldrich syndrome (X-linked)

o HIV

o X-linked lymphoproliferative syndrome

• Lung nodules

o Variable in size

o Bilateral

o Involve mid and lower lung fields

o Larger nodules

§ Exhibit central necrosis

§ Cavitation often present

• Kidney and brain

o Nodular lesions

o Also central necrosis

• Skin lesions: nodules and papules in dermis and subcutaneous tissue (~85%) sometimes with necrosis and ulceration. Cutaneous plaques or maculopapular rash (~15%). EBV positivity less often seen (especially in plaque lesions)

• Microscopy: angiocentric and angiodestructive polymorphous lymphoid infiltrate. Polymorphous lymphoid infiltrate: predominance of reactive T-cells, B-cells with some atypia, plasma cells, histiocytes.

EBV-positive B-cells

• Small numbers

• Some atypia

• May resemble immunoblasts

• May resemble Hodgkin cells

• May be multinucleated

• Prominent vascular changes

o Lymphocytic vasculitis

• May compromise vascular integrity, leading to infarction

o Fibrinoid necrosis

• Common

• Mediated by EBV-induced chemokines

• Grading: Lipford grading scheme

o Three histologic grades

o Based on proportion of EBV-positive B-cells relative to reactive lymphocytic background

o Larger numbers of atypical lymphoid cells associated with worse prognosis

Grade 1

o Polymorphous lymphoid infiltrate

o Absent or rare large transformed cells (<5/HPF EBV-positive cells by in situ hybridization)

o Necrosis not prominent

Grade 2

o Polymorphous lymphoid infiltrate

o 5-20 EBV-positive cells/HPF

o Necrosis more commonly seen

Grade 3

o Readily identified as malignant lymphoma on histology

o Numerous large lymphoid cells (but inflammatory background is still present)

o Numerous EBV-positive cells (>20/HPF)

o Markedly pleomorphic and Hodgkin-like cells are often present

o Necrosis is usually extensive

Grade 3 lesions

o Subtype of DLBCL

o However, some cases may spontaneously regress

Immunophenotype

· B cells:

o EBV positive

o LMP1 usually positive in larger atypical cells

o CD20 positive

o CD79a and CD30 variably positive

o CD15 negative

o Monoclonal cytoplasmic Ig expression only rarely seen

· Background reactive T-lymphocytes

o CD3 positive

o CD4-positive

o CD8-positive cells very few in number

• Genetics:
Most Grade 2 or 3 disease

o Clonal Ig genes

o Different clones may be identified in different anatomic sites

Grade 1 disease

o Demonstration of clonality is inconsistent

• Rare EBV-positive cells, or

• polyclonal

• Prognosis: variable natural history

o Median survival <2 years in most patients

o Waxing and waning with spontaneous remission in some patients

• Grade 1 and 2 disease may respond to Interferon 2b

• Grade 3 disease may respond to aggressive chemotherapy

• Most common cause of death is progressive pulmonary disease