Germ cell tumors in monozygous twins with gonadal dysgenesis and 46,XY karyotype.

Monozygous twin phenotypic females, aged 18, with primary amenorrhea and a 46,XY karyotype and bearing germ cell tumors are described. Patient 1 had a large pelvic tumor involving the uterus, oviduct, and intestine. Histology revealed the choriocarcinoma pattern. No ovarian or testicular tissue was identified. The preoperative serologic pregnancy test was positive. After surgery the urinary human chorionic gonadotropin value was 2500 units per 24 hours. The patient died 2 months after the operation despite chemotherapy. Patient 2 was admitted to the hospital for evaluation following the discovery of pelvic tumor in her twin sister. She had 1 streak gonad harboring gonadoblastoma and, on the opposite side, a gonadoblastoma overgrown by dysgerminoma. The patient is well 4 years after surgery. The risk of malignancy in individuals with XY gonadal dysgenesis is emphasized, and examination and confirmation of karyotype of siblings are recommended.