Malignant sex cord stromal tumor (SCST) of ovary is a rare ovarian cancer (see this term) arising from granulosa, theca, sertoli and leydig cells or stromal fibroblasts, occurring at any age and presenting with abdominal or pelvic mass, and characterized (with the exception of fibroma) by the production of sex steroids resulting in manifestations of hormone excess, with a relatively favorable prognosis.