Contribution of Immunocytochemistry to the Diagnosis of Usual and Unusual Lymphoma Cases

Some of the limitations of fine needle aspiration (FNA) in the cytodiagnosis of lymphoma include problems encountered in differentiating reactive hyperplasia from low-grade non-Hodgkin lymphoma (NHL), lower cytodiagnostic accuracy for NHL with a follicular (nodular) pattern and nodular sclerosis type of classical Hodgkin lymphoma (HL), and overlapping morphological features between T-cell-rich B-cell lymphoma (TCRBCL), anaplastic large cell lymphoma (ALCL), and HL. Immunocytochemistry may be of help in such situations. The B-cell lymphomas such as small lymphocytic lymphoma/CLL, follicular lymphoma (FL), mantle cell lymphoma (MCL), MALT lymphoma, Burkitt lymphoma (BL), and diffuse large B-cell lymphoma (DLBCL) have pan-B-cell markers (CD19, CD20, CD22, CD23, and CD79a). The FL (centrocytic), MCL, and MALT lymphoma can be differentiated with the use of a panel consisting of CD5, CD10, and CD23. In addition, FL is BCL2+ and MCL is BCL2+ as well as cyclin D1+. The DLBCL is BCL6+ in 60–90% cases. Besides pan B-cell marker, the immunocytochemical profile of BL includes CD10+, BCl6+, EBV±, and Ki67+ (100% cells). TCRBCL, a rare variant of DLBCL can be immunocytochemically differentiated from anaplastic large cell lymphoma (CD45+, CD30+, CD15‒, T±, B‒, EMA+, ALK1±) and classical HL (CD30+, CD15+, CD45‒, B‒, T‒, EMA‒). Unlike classical HL, the nodular lymphocytic predominant HL has a phenotype that includes LCA+, CD20+, CD79a+, CD15‒, and CD30‒. Whereas the immature neoplastic cells of T-lymphoblastic lymphoma (LBL) are CD3+, CD20‒, and Tdt+, the rarely encountered mature T-CLL/T-PLL are immunophenotypically CD3+, CD4+, CD5+, CD7+, CD8‒, CD20‒, CD23‒, and Tdt‒.