C-ERBB-2 ONCOPROTEIN IMMUNOSTAINING IN SEROUS EFFUSIONS

The product of c-erbB-2 gene is detected in a proportion of carcinomas from various sites and is generally associated with a high degree of malignancy. A series of 58 effusions containing malignant cells and 16 cytologically negative serous effusions was assessed by immunocytoche mical methods for c-erbB-2 expression using the monoclonal antibody NC L-B11, which recognizes the internal domain of the c-erbB-2 oncoprotei n. Both alcohol-fixed smears and cell blocks from formalin-fixed speci mens were used. A crisp, clear cut membrane-associated positive staini ng was evident in 51% (30/58) malignant effusions and was restricted t o metastatic adenocarcinomas. Breast and ovarian cancers showed the hi ghest incidence of positivity. Mesotheliomas as well as non-neoplastic effusions were consistently negative. Paraffin blocks from formalin-f ixed cells displayed a weak immunoreactivity when compared with their alcohol-fixed counterparts. The study shows that the c-erbB-2 oncoprot ein can be easily identified in standard cytological smears: it can be of assistance in differentiating adenocarcinomas from mesotheliomas, and in selected cases it can provide a further prognostic indicator, r eplacing tissue immunohistochemistry.