Ovarian steroid cell tumor, not otherwise specified (NOS): an unusual case with myelolipoma

Myelolipoma is an uncommon lesion composed of mature fat and hematopoietic cells. Extra-adrenal myelolipoma is rare. We report an unusual case of concurrent myelolipoma in a steroid cell tumor in a 21-year-old woman with virilization. She had a 6-year secondary amenorrhea history. Her serum testosterone level was elevated (16.2-24.9 nmol/L). Transvaginal ultrasound and computed tomography showed a solid round pelvic mass. The left ovarian mass was grossly well encapsulated with a tan-to-dark-brown, vaguely nodular cut surface. Microscopically, the tumor was characterized by large aggregates of cells resembling typical hormone-secreting cells and the stroma was composed of mature fat and rich hematopoietic cells representing all 3 hematopoietic cell lineages. Immunohistochemistry showed that the tumor cells were strongly positive for α-inhibin and Melan-A. Lineage-specific markers including myeloid peroxidase were variably expressed in hematopoietic cells. This rare case will expand our appreciation of the spectrum and histogenesis of ovarian tumors.