Non-Leydig sex-cord tumors of the testis. The place of immunohistochemistry in diagnosis and prognosis. A study of twenty cases

In 20 sex-cord tumors of the testes, we investigated immunohistochemistry as a possible method for histopathological diagnosis and evaluation of prognosis. We examined the following molecules: inhibin, CD99, cytokeratin, vimentin, MIB-1, estrogen receptors and progesterone receptors. These tumors of the testes comprised 18 Sertoli cell tumors (ScT) and two undifferentiated sex-cord tumors (USCT). Four tumors have been considered as malignant, because of metastatic spread. Inhibin was expressed by the tumor cells in 80% of sex cord tumors, without any correlation to the degree of differentiation and only in 25% of the malignant cases. Inhibin is a specific marker for sex-cord tumors of the testis and is particularly useful for the diagnosis of USCT. CD99, vimentin, keratin, progesterone and estrogen receptors were expressed in, respectively, 60%, 75%, 35%, 65% and 20% of cases; 95% expressed one of the three following markers: inhibin, CD99 or vimentin. Proliferation index MIB-1 was equal to or higher than 30% in the four malignant cases versus less than 20% in other cases. Lack of inhibin expression and a proliferation index (MIB-1) greater than 30% should be considered as a criterion in favor of malignancy.