BCL-2 DISTRIBUTION IN NEUROEPITHELIAL TUMORS - AN IMMUNOHISTOCHEMICALSTUDY

Bcl-2 proto-oncogene prevents apoptosis in many conditions. First dete cted in lymphomas, it has been also described in non-lymphoid tissues. The immunohistochemical distribution of bcl-2 protein in 100 neuroepi thelial tumors is presented. Bcl-2 was positive in some neurons of nor mal nervous tissue, in reactive astrocytes and variably in all neuroep itelial tumors. The reaction product was either diffuse or granular, d ue to bcl-2 protein localization on cytoplasmic, nuclear and mitochond rial membranes. The positivity was high in medulloblastomas and in ast rocytic tumors. In the latter, the strongest staining was found in cel ls retaining the astrocytic aspect. Oligodendroglial cells were minima lly stained. No correlation of bcl-2 staining with survival was found in each tumor type. The interpretation of the results is based on the one side on the constitutive role played by bcl-2 in the nervous tissu e and its neoplastic derivatives. On the other side, in tumors bcl-2 a cts by preventing tumor cells from undergoing apoptosis. Bcl-2 express ion in brain tumors, therefore, receives a dual interpretation. For th is reason and for the lacking of correlation with survival, bcl-2 expr ession cannot be regarded as a prognostic factor.