Bcl-2, Bcl-6 and CD10 expression in cutaneous B-cell lymphoma: further support for a follicle centre cell origin and differential diagnostic significance

Background Primary cutaneous follicle centre cell lymphomas (PCFCCLs) are the most common type of cutaneous B-cell lymphoma. There is ongoing discussion on the origin of the neoplastic B cells in these PCFCCLs, and consequently on their relation to the groups of primary cutaneous marginal zone B-cell lymphomas (PCMZLs) and nodal follicular lymphomas. Objectives To define better the neoplastic B cells in PCFCCLs, and to find out if differences in the expression of the antiapoptopic protein Bcl-2, and Bcl-6 and CD10, molecules which are normally expressed by the neoplastic B cells in nodal follicular lymphomas, might have diagnostic or prognostic significance in cutaneous B-cell lymphoproliferative disorders. Methods Pretreatment biopsies of well-defined groups of PCFCCL (n = 24), PCMZL (n = 14), primary cutaneous large B-cell lymphoma of the leg (PCLBCL-leg; n = 19), secondary cutaneous follicular lymphoma (n = 3) and cutaneous pseudo-B-cell lymphoma (n = 6) were investigated by immunohistochemistry for expression of Bcl-2, Bcl-6 and CD10. Results The PCFCCLs consistently expressed Bcl-6, whereas CD10 and Bcl-2 were expressed in only one and two of 24 cases, respectively. In contrast, PCMZLs were always negative for Bcl-6 and CD10, but were Bcl-2 positive, whereas skin and lymph node localizations of secondary cutaneous follicular lymphomas consistently expressed all of Bcl-2, Bcl-6 and CD10. Reactive follicle centre cells in pseudo-B-cell lymphomas expressed Bcl-6 (six of six cases) and CD10 (five of six cases), but not Bcl-2. PCLBCL-leg was Bcl-6 positive and CD10 negative in all cases, irrespective of clinical outcome, and strongly expressed Bcl-2 protein in all but two cases. Conclusions The results of the present study provide further support for the follicle centre cell origin of both PCFCCL and PCLBCL-leg, and indicate that staining for Bcl-2, Bcl-6 and CD10 can serve as an important adjunct in the differential diagnosis of cutaneous B-cell lymphoproliferative disorders.