Immunohistochemical analysis of sox9 in ovarian Sertoli cell tumors and other tumors in the differential diagnosis.

The distinction of ovarian Sertoli cell tumor from other tumors in the histological differential diagnosis, particularly endometrioid carcinoma and carcinoid tumor, may be difficult. Many immunohistochemical markers have been studied for this differential diagnosis, but currently available markers are neither 100% sensitive nor specific. Sox9 is a transcription factor involved in Sertoli cell differentiation in the testis. The role that this molecule plays in the pathogenesis of ovarian Sertoli cell tumors and the potential use as an immunohistochemical marker for differential diagnosis have not been investigated. Immunohistochemical staining for Sox9 was performed in 152 ovarian tumors: pure Sertoli cell tumor (n = 36), endometrioid borderline tumor (n = 38), well-differentiated endometrioid carcinoma (n = 26), sertoliform endometrioid carcinoma (n = 13), and carcinoid tumor (n = 39). Nuclear expression was considered positive. Extent and intensity of staining were semiquantitatively scored. In addition, immunohistochemical composite scores in positive cases (ranging from 1 to 12) were calculated based on the extent score multiplied by the intensity score. Sox9 was expressed in 44% of Sertoli cell tumors, 55% of endometrioid borderline tumors, 65% of well-differentiated endometrioid carcinomas, 39% of sertoliform endometrioid carcinomas, and 10% of carcinoid tumors. The mean Sox9 immunohistochemical composite scores in positive cases were 6.3 for Sertoli cell tumor, 5.3 for endometrioid borderline tumor, 8.0 for well-differentiated endometrioid carcinoma, 2.8 for sertoliform endometrioid carcinoma, and 6.8 for carcinoid tumor. The differences in the mean Sox9 composite scores between Sertoli cell tumor and the other tumor categories were not statistically significant (p values ranged from 0.092 to 0.523). We conclude that Sox9 is variably expressed in ovarian Sertoli cell tumor and other tumors that are in the differential diagnosis and, thus, is not helpful for immunohistochemical distinction. Understanding the role of Sox9 in the pathogenesis of ovarian Sertoli cell tumor requires further study.