S-100 protein in ovarian tumors. A comparative immunohistochemical study of 135 cases

The distribution of S-100 protein in 135 ovarian tumors, of which 127 were epithelial, was investigated using the immunoperoxidase method. S-100 protein has been demonstrated previously in tumors of various origins. The present study further revealed its characteristic distribution in common epithelial tumors of the ovary. S-100 protein was present in 69% of serous tumors (benign, 50%; borderline, 100%; malignant, 71%), as well as in the serous elements of serous & mucinous mixed tumors (30%). S-100 protein was also demonstrated in 25% of clear cell carcinomas and 29% of endometrioid carcinomas. Interestingly, none of the mucinous tumors were positive for S-100 protein. In addition, the expression of S-100 protein by epithelial ovarian tumors was compared with that of CA 125 and carcinoembryonic antigen (CEA). The distribution of S-100 protein was similar to that of CA 125, since both antigens were frequently present in serous tumors, although their expression patterns were different. On the other hand, S-100 protein-positive cases were almost negative for CEA or vice versa. Our observations indicate that demonstration of S-100 protein in common epithelial tumors of the ovary and comparison of S-100 protein distribution with that of CA 125 and CEA may further clarify the characteristics of common epithelial tumors of the ovary.