Disorders of sex development (DSD), previously termed intersex, are uncommon, and are usually, but not always, diagnosed at birth. Issues of gender assignment, psychosexual development and the potential for malignant change in a dysgenetic gonad need to be considered. Here, we report a rare presentation of advanced malignancy in an abdominal gonad associated with the formation of a uterus in an adult male with a previously undiagnosed DSD.