Ovarian sex cord-stromal tumors: an immunohistochemical study including a comparison of calretinin and inhibin.

Because ovarian sex cord-stromal tumors (SCST) are morphologically heterogeneous neoplasms that are relatively infrequently encountered, their diagnosis can be difficult. Immunohistochemical staining may be useful for establishing the diagnosis in problematic cases. We studied 53 ovarian SCSTs to characterize their immunohistochemical staining pattern: 17 adult granulosa cell tumors (AGCTs), 4 juvenile granulosa cell tumors (JGCTs), 3 sex cord tumors with annular tubules (SCTATs), 9 Sertoli-Leydig cell tumors (SLCTs), 10 fibromas, 5 fibrothecomas (FTs), and 5 thecomas. In 8 of the 53 cases, the tissue studied was from a metastatic site. The immunopanel included calretinin, inhibin, WT1, cytokeratin cocktail, epithelial membrane antigen (EMA), and cytokeratin 5/6 (CK5/6). The fibromas and FTs were also tested with CD10. The extent of staining was assessed in a semiquantitative fashion and ranked on a scale of 0 through 4+. All of the tumors, except for 1 metastatic SLCT, were positive for calretinin. Forty-five of the cases (85%) stained for inhibin; 1 metastatic AGCT, 3 fibromas, and 4 FTs were negative. WT1 was present in 39 tumors (74%), with expression most prominent in the SLCTs. The cytokeratin cocktail stained 23 of the 53 tumors (43%), whereas just 1 tumor was positive for EMA (1+ in a JGCT). All tumors were negative for CK5/6, and the 15 fibromas and FTs were negative for CD10. We conclude that because cytokeratin is frequently expressed by SCSTs, in particular by granulosa cell tumors, SLCTs, and SCTATs, the inclusion of EMA in a panel may help to exclude epithelial neoplasms. In addition, WT1, present in normal granulosa cells, is expressed by a majority of SCSTs. Finally, these results demonstrate that calretinin is at least as sensitive as inhibin for ovarian SCSTs overall and that it is more sensitive than inhibin for fibromas and FTs.