IMMUNOHISTOCHEMICAL EXPRESSION OF BCL-2 IN MELANOMAS AND INTRADERMAL NEVI

The BCL-2 gene is the prototype of a newly described family of oncogen es involved in tumorigenesis by blocking apoptosis, or programmed cell death. Overexpression of BCL-2 protein was originally described in fo llicular B-cell lymphomas bearing the 14;18 translocation. BCL-2 overe xpression has also been described in other lymphomas and more rarely i n neoplasms outside the lymphoid tissue. The aim of this paper is to d etermine the immunohistochemical expression of BCL-2 in intradermal ne vi and primary invasive and metastatic melanoma. Formalin-fixed and pa raffin-embedded tissues from 4 cutaneous melanoma metastases, 10 prima ry invasive melanomas, and 10 intradermal melanocytic nevi were immuno labeled with monoclonal antibodies directed against BCL-2 protein (Dak o, clone 124) and Ki-67 antigen (Amac, clone MIB-1), after antigen ret rieval techniques. Morphologically normal epidermal melanocytes expres sed BCL-2, as did nevi and melanomas in virtually all cells. However, whereas the labeling in normal melanocytes and nevus cells showed a un iformly strong reactivity, melanoma cells showed a variable but mainly weak reactivity. Ki-67 antigen expression was restricted to melanomas . The widespread expression of BCL-2 suggests that this oncoprotein ca nnot be involved in the malignant transformation of melanocytic cells. It seems likely that the decreased BCL-2 expression detected in melan omas may reflect one further step of tumor progression in melanocytic neoplasms.