Stromal overgrowth in a brenner tumor or ovarian fibroma with minor sex cord elements?

Computed tomography obtained as part of a urinary tract assessment in a 68-year-old woman incidentally detected a solid adnexal mass. Bilateral salpingo-oophorectomy revealed a unilateral, 4-cm, white to tan-yellow colored, focally calcified, left ovarian mass. Microscopically, the tumor was composed of bland fibroblasts, abundant collagen, and areas of calcification with a minor component composed of nests of epithelial cells with nuclear clefts focally evident, some of which contained central lumens with eosinophilic secretions. The major considerations were fibromatous overgrowth in a Brenner tumor or ovarian fibroma with minor sex cord elements. Immunostains for cytokeratin 7 showed diffuse positivity in the epithelial nests, whereas cytokeratin 20 and inhibin were negative, further supporting the diagnosis of a Brenner tumor.