Uterine horn hematometra simulating a “Gonadal” mass in a gonadectomized XO female

Abstract A 16½-year old girl with mixed gonadal dysgenesis was born with ambiguous genitalia and had undergone bilateral gonadectomy in infancy. She developed a right adnexal mass and recurrent right lower abdominal pain after starting cyclical replacement estrogen and progesterone therapy. The location and characteristics of the mass raised concern that a neoplasm had developed from a portion of the dysgenetic gonad which might not have been removed during the original surgery. Upon exploratory laparotomy, the right adnexal mass was observed to be a hematometra of a rudimentary uterine horn that had become distended with blood. The uterine horn was removed and the uterus was left undisturbed.