Rare benign tumor consisting of a combination of mixed germ cells and sex cord stroma derivatives (Sertoli-like and granulosa-like cells), commonly arising in dysgenetic gonads. Occurs in males and phenotypic females with a Y chromosome. Tumors may produce excess testosterone or estrogen, causing findings such as abnormal genitalia, amenorrhea, virilization, and pelvic mass. Unilateral or bilateral. Most frequently diagnosed before the third decade. Lesion sizes vary from 1 mm up to 20 cm. May calcify. Associated with abnormal karyotype. Patients are at risk for developing a malignant germ cell tumor.