IMMUNOHISTOCHEMICAL DETECTION OF RAS P21 ONCOPROTEIN IN UNDIFFERENTIATED AND WELL-DIFFERENTIATED EPITHELIAL CARCINOMAS OF THE HUMAN OVARY

Expression of ras p21 oncoproteins in human ovarian carcinomas was exa mined immunohistochemically by using a monoclonal antibody(clone RAS 1 0) with respect to the degree of their histological differentiation. T o acheive this, the intensity of staining for the protein was compared between undifferentiated and well differentiated carcinomas, i.e. ext reme subtypes of common epithelial carcinomas. The former was composed of 8 ''solid'' carcinomas and the latter; 11 serous, 8 mucinous, 4 en dometrioid and 4 clear cell carcinomas. All the cases examined includi ng both undifferentiated and well-differentiated carcinomas, showed a positive reaction to this antibody. Staining intensity and the number of positive cells somewhat varied among rite cases. Additionally, 2 ca ses of ovarian epithelial tumors of low malignant potential(I,MP) were stained with this antibody. Both the cases were positive, but the num ber of positive cells seemed to be rather less than that found in the carcinoma groups. Thus, no differences in ras p21 expression were obse rved between the cases examined in spire of the differences in the deg ree of differentiation of the epithelial ovarian carcinomas. However, the possibility remained that the number of positive cells could be an indicator of malignant potential, enabling us to distinguish LMPs fro m carcinomas. Thus immunodetection of I ras p21 could not provide an a dditional means for the histological differentiation of ovarian cancer ; although the evaluation of basement membrane integrity and cell prol iferation kinetics as reported previously was useful in differential d iagnosis and in uncle,standing the biology of ovarian undifferentiated carcinomas.