Diagnostic clues and pitfalls in small B-cell lymphomas.
| Lymphoma Subtype . | Diagnostic Clues . | Pitfalls . |
|---|---|---|
| Abbreviations: LEL, lymphoepithelial lesion; SLL, small lymphocytic lymphoma; CLL, chronic lymphocytic leukemia; MZL, marginal zone lymphoma; PB, peripheral blood; BM, bone marrow; FL, follicular lymphoma; PCR, polymerase chain reaction; FISH, fluoresence in situ hybridization; RFH, reactive follicular hyperplasia; FDC, follicular dendritic cell | ||
| Follicular lymphoma | Follicle formation, admixed centroblasts, presence of tight FDC meshworks –CD10 +/− Bcl-6 expression between follicles –Low proliferative rate in contrast to RFH –PCR/FISH presence of t(14;18) | Not all FLs express Bcl-2 protein –BCL2 PCR can be negative (inherent high false- negative rate) –Discordance between morphology and proliferative rate in some cases |
| MALT lymphoma | Reactive follicles, LELs and centrocyte-like cells –Presence of light chain restriction –Absence of CD5/CD10 expression –FISH detection of characteristic translocations | Classic cytomorphology not always present –Small biopsies may produce false-positive PCR for IGH clonality –Distinction from LPL may be difficult |
| SLL | Presence of growth centers –Co-expression of CD5 and CD23 –Absence of t(11;14) | Growth centers may be ill-defined |
| Splenic MZL | Biphasic splenic morphology –Uncommon red pulp pattern –Frequent PB/BM involvement, may be intrasinusoidal in BM –Cells fail to express CD5, CD10, CD23 and CD43 | Occasional SMZL cases express CD5 –Some may weakly express CD23 –Diagnosis can be difficult without a splenectomy |
| Nodal MZL | Distinct marginal zone architecture –Rule out adjacent mucosal disease –B cells do not co-express CD5 or CD10 | Almost a diagnosis of exclusion –Absence of characteristic cytogenetic alterations found in MALT lymphomas |
| Lymphoplasmacytic lymphoma | Mature plasma cell component +/− Russell/Dutcher bodies –Usually not leukemic –Absence of growth centers and CD5 expression –Increased mast cells in BM –Presence of serum/urine monoclonal protein | Subtle inter-follicular pattern in some cases –Grey-zone cases with SLL/CLL occur –Clinical information often not available |
| Mantle cell lymphoma | Monomorphic appearance, absence of centroblasts; epithelioid histiocytes and mitoses –PB & BM often involved –CD5+, CD23− –Expression of cyclin D1 –Presence of t(11;14) | Blastoid variants may be pleomorphic Rare cases mimic MZL architecture –5% to 7% may be CD5− –Rare cases lack t(11;14) and cyclin D1 overexpression |
| Lymphoma Subtype . | Diagnostic Clues . | Pitfalls . |
|---|---|---|
| Abbreviations: LEL, lymphoepithelial lesion; SLL, small lymphocytic lymphoma; CLL, chronic lymphocytic leukemia; MZL, marginal zone lymphoma; PB, peripheral blood; BM, bone marrow; FL, follicular lymphoma; PCR, polymerase chain reaction; FISH, fluoresence in situ hybridization; RFH, reactive follicular hyperplasia; FDC, follicular dendritic cell | ||
| Follicular lymphoma | Follicle formation, admixed centroblasts, presence of tight FDC meshworks –CD10 +/− Bcl-6 expression between follicles –Low proliferative rate in contrast to RFH –PCR/FISH presence of t(14;18) | Not all FLs express Bcl-2 protein –BCL2 PCR can be negative (inherent high false- negative rate) –Discordance between morphology and proliferative rate in some cases |
| MALT lymphoma | Reactive follicles, LELs and centrocyte-like cells –Presence of light chain restriction –Absence of CD5/CD10 expression –FISH detection of characteristic translocations | Classic cytomorphology not always present –Small biopsies may produce false-positive PCR for IGH clonality –Distinction from LPL may be difficult |
| SLL | Presence of growth centers –Co-expression of CD5 and CD23 –Absence of t(11;14) | Growth centers may be ill-defined |
| Splenic MZL | Biphasic splenic morphology –Uncommon red pulp pattern –Frequent PB/BM involvement, may be intrasinusoidal in BM –Cells fail to express CD5, CD10, CD23 and CD43 | Occasional SMZL cases express CD5 –Some may weakly express CD23 –Diagnosis can be difficult without a splenectomy |
| Nodal MZL | Distinct marginal zone architecture –Rule out adjacent mucosal disease –B cells do not co-express CD5 or CD10 | Almost a diagnosis of exclusion –Absence of characteristic cytogenetic alterations found in MALT lymphomas |
| Lymphoplasmacytic lymphoma | Mature plasma cell component +/− Russell/Dutcher bodies –Usually not leukemic –Absence of growth centers and CD5 expression –Increased mast cells in BM –Presence of serum/urine monoclonal protein | Subtle inter-follicular pattern in some cases –Grey-zone cases with SLL/CLL occur –Clinical information often not available |
| Mantle cell lymphoma | Monomorphic appearance, absence of centroblasts; epithelioid histiocytes and mitoses –PB & BM often involved –CD5+, CD23− –Expression of cyclin D1 –Presence of t(11;14) | Blastoid variants may be pleomorphic Rare cases mimic MZL architecture –5% to 7% may be CD5− –Rare cases lack t(11;14) and cyclin D1 overexpression |