An ovarian or testicular stromal tumor characterized by the presence of lipid-rich neoplastic spindle cells. In females, uterine bleeding is the most common symptom. A minority of post-menopausal women with thecoma have an associated endometrial adenocarcinoma or rarely a malignant mixed mullerian tumor or endometrial stromal sarcoma. Rare cases with nuclear atypia and mitotic activity may metastasize. In males, thecomas are rare and they usually present as slow growing, sometimes painful masses. Metastases have not been reported. [from
NCI]