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ABSTRACT: PAX-5 is a B cell specific transcription factor crucial for B cell ontogeny and has been detected in most of human B-cell lymphomas. In mouse, PAX-5 is also highly expressed in the central nervous system under tight temporal and spatial controls during embryogenesis. In humans, however, detection of PAX-5 in cells other than B lymphocytes has rarely been reported. We have encountered cases of Merkel cell carcinoma expressing PAX-5 during our routine evaluation of lymphoma. Because Merkel cell carcinoma is a small blue round cell tumor constantly in the differential diagnosis of lymphoma, we expanded our study in an effort to determine if PAX-5 is significantly expressed in neuroendocrine tumors. Based on our immunohistochemistry results using a monoclonal anti-PAX5 antibody with paraffin-embedded tissue sections, we report herein that PAX-5 was detected in 29 of 31 (93.5%) of Merkel cell carcinoma and 22 of 30 (73.3%) of small cell carcinoma, but in none of 17 cases of carcinoid tumor. Furthermore, the staining intensity of PAX-5 in Merkel cell carcinoma was frequently comparable with that in most B-cell lymphomas. We conclude that expression of PAX-5 is not confined to the B cell lineage and is frequently associated with neuroendocrine carcinomas.
American Journal of Surgical Pathology 06/2005; 29(5):687-92. · 4.35 Impact Factor
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ABSTRACT: The characteristic histologic features and immunophenotype are usually diagnostic and allow distinguishing CD30 positive T-cell lymphoma (including anaplastic large cell lymphoma) from classical Hodgkin's lymphoma. The latter differs by expression of CD15 and lack of CD45, pan-T antigens and ALK expression. We report nine cases of large cell hematopoietic neoplasms in which the neoplastic cells co-expressed CD30 and CD15, and had immunophenotypic and morphologic features of T-cell lymphoproliferative process. The average age of the CD15-positive group was 61.9 years; 6 cases occurred in men and 3 in women. The tumors were located in lymph nodes in 8 cases, and in liver in 1 case. Two cases expressed ALK protein. There were no statistically significant differences in phenotypic parameters between the CD15-positive and CD15-negative neoplasms (p>0.05). However, the CD15-positive group appeared to show a minor trend toward less positivity for EMA (44% versus 72%), ALK protein (22% versus 51%), and CD45RO (33.3% versus 83.3%, p=0.07), when compared to the typical CD15-negative neoplasms. In summary, although the co-expression of CD30 and CD15 is typical for classical HL, it may be also present in a subset of peripheral T-cell neoplasms including ALK-positive anaplastic large cell lymphoma. Combined and sensible use of morphology and a broad immunophenotypic panel in cases with limited material and/or those with overlapping histologic patterns will best discriminate between HL and ALCL. It is incumbent upon the pathologist to distinguish between these two clinicopathologic entities, since treatment options and clinical outcomes differ.
International Journal of Oncology 03/2003; 22(2):319-24. · 2.40 Impact Factor
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ABSTRACT: Coexpression of CD5 and CD10 is highly unusual in B-cell lymphomas and may pose a diagnostic challenge. We report 42 cases of B-cell lymphoma with simultaneous expression of CD5 and CD10. They made up approximately 0.4% of all B-cell lymphomas seen during the study period and included the following cases: large B-cell lymphoma (LBCL), 14 (33%); follicular lymphoma (FL), 10 (24%); mantle cell lymphoma (MCL), 9 (21%); chronic lymphocytic leukemia, 4 (10%); acute precursor B-cell lymphoblastic leukemia/lymphoma, 2 (5%); and other low-grade B-cell lymphomas, 3 (7%). All MCLs had overexpression of bcl-1 or the t(11;14) and were CD43+. All FLs had typical histomorphologic features and were bcl-2+ and bcl-6+ but CD43-. Of 14 LBCLs, 5 were histologically high-grade. Six (43%) of 14 patients with LBCL died within 10 months of diagnosis of CD5+CD10+ lymphoma (median survival, 4 months), including all 3 patients with stage IV disease and 2 of 5 with histologically high-grade lymphoma. Our findings indicate that coexpression of CD5 and CD10 is rare but occurs in diverse subtypes of B-cell lymphoma. Investigation of bcl-1, bcl-6, and CD43 and morphologic evaluation may resolve the potential confusion in diagnosis and lead to the recognition of the correct lymphoma subtype.
American Journal of Clinical Pathology 03/2003; 119(2):218-30. · 2.60 Impact Factor
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ABSTRACT: Mantle cell lymphoma (MCL) typically expresses B-cell antigens and CD5 and overexpresses bcl-1 protein. However, unusual cases of bcl-1+ and CD5-MCL have been observed, posing a practical challenge for correct diagnosis and management. We identified 25 cases (48 samples) of bcl-1+ and CD5- lymphoma. CD5 expression was assessed by flow cytometric analysis alone (1 case), immunohistochemical analysis alone (17 cases), or dual flow cytometric/immunohistochemical methods (7 cases). The morphologic features were consistent with MCL with centrocytic cytomorphology in 20 cases and blastic variant in 5 cases. The t(11;14) was confirmed in 8 of 11 cases by fluorescence in situ hybridization of paraffin-embedded tissue. Cytogenetic analysis revealed the t(11;14) within a complex karyotype in 2 additional cases. These data show that MCL may lack CD5 expression. Evaluation of bcl-1 expression by immunohistochemical analysis or molecular genetics may be indicated if MCL is suspected clinically or morphologically despite a lack of CD5 expression.
American Journal of Clinical Pathology 09/2002; 118(2):216-24. · 2.60 Impact Factor
