This is a case of a young woman who had testicular feminization syndrome and developed a seminoma in an undescended intrapelvic testis. Androgen insensitivity (testicular feminization) syndrome is a rare inherited form of male pseudohermaphroditism that occurs in phenotypically normal women with adequate breast development, normal external genitalia, a vagina of variable depth, absent uterus, and sparse or absent pubic and axillary hair. The gonad (undescended testes) may be intraabdominal, inguinal, or labial. These patients characteristically have male karyotype (XY) and negative sex chromatin and are at increased risk of undergoing malignant transformation of the undescended gonad. We review the literature emphasizing the biochemical and endocrinologic abnormalities leading to the syndrome, as well as the morphologic abnormalities (light microscopic) of the undescended testes, diagnosis, and therapeutic management.