A Rare Variant of Ovarian Fibroma With Minor Sex Cord Elements: A Unique Expression of Stromal Differentiation.

Ovarian fibroma with minor sex cord elements is a rare and underrecognized histological variant of ovarian stromal tumors. While the bulk of the tumor resembles a classic fibroma, the presence of small foci of sexcord-like cells can create a diagnostic dilemma, particularly in limited samples. This tumor exhibits hormonal production resulting in endometrial hyperplasia, polyp, or even carcinoma. We report the case of a 56-year-old postmenopausal woman who presented with a history of intermittent postmenopausal bleeding and lower abdominal discomfort with primary infertility. There was a slowly enlarging pelvic mass discovered incidentally on ultrasound imaging. Surgical excision revealed a firm, white encapsulated ovarian tumor. Histologically, the lesion was composed of interlacing bundles of bland spindle cells, characteristic of a fibroma. Notably, scattered discrete clusters and cords of cells resembling Granulosa or Sertoli-type differentiation were observed, occupying less than 10% of the tumor area. These minor sex cord elements exhibited uniform round to oval nuclei and scant cytoplasm, without atypia or mitotic activity. Immunohistochemistry supported the diagnosis, with calretinin and inhibin positivity in the sex cord foci, while the stromal component showed SMA positivity. We report this case because of its rarity and its silent clinical presentation.