Answer: Endometrioid carcinoma, sertoliform variant

Histology: The tumor is composed of cords and ribbons of columnar cell cells infiltrating ovarian stroma. In foci, the cells form confluent aggregates. Moderate cytologic atypia and rare mitotic figures are identified.

Discussion: This neoplasm resembles Sertoli-Leidig cell tumor of intermediate differentiation. Examination of stroma surrounding the cords and tubules reveals lack of Leidig cells. Positive labeling with EMA and no expression of inhibin and calretinin help in this differential. Carcinoid tumors usually contain longer and thicker ribbons and cords that are more evenly distributed in the stroma. The cells contains round to ovoid uniform nuclei with finely dispersed chromatin. Primary carcinoid tumors are often associated with other teratomatous elements; therefore, extensive sampling of the neoplasm is warranted. Metastatic carcinoids are usually bilateral; these patients often have a history of carcinoid tumor elsewhere. Metastatic carcinoma, particularly from breast can be excluded with lack of expression of GCDFP and mammaglobin and labeling with Pax8.