Adrenal rest tumor of the broad ligament: case report with immunohistochemical study of steroidogenic enzymes.

An adrenal rest tumor of the broad ligament was studied in a 43-year-old woman. The tumor measuring 6 x 3 x 3 cm and appearing as golden-yellow on the cut surface was incidentally discovered during a total hysterectomy due to uterine leiomyoma. The encapsulated tumor was predominantly composed of pale and lipid-rich cells arranged in alveolar clusters or short blunt cords. Electron microscopic examination revealed mitochondria with tubulo-vesicular cristae and abundant lipid droplets. Adrenal 4-binding protein, a transcriptional factor of steroidogenesis, was present in almost all of the tumor cells, suggestive of steroidogenic features in the lesion. Immunoreactivity of steroidogenic enzymes involved in adrenocortical steroid production was detected in the tumor cells, suggesting that tumor cells had the potential to synthesize adrenocortical steroids. A relatively low Ki-67 labelling index (3.20 +/- 1.15 per 100 tumor cells) and an absence of necrosis and vascular and/or capsular invasion suggest benignity of the lesion.