Somatically Derived Yolk Sac Tumor of the Ovary in a Young Woman.

Ovarian carcinoma with a somatically derived yolk sac tumor component is a phenomenon known to mostly occur in postmenopausal women. Herein, we report an ovarian endometriosis-associated somatic yolk sac tumor arising in the background of a low-grade endometrioid adenocarcinoma in a young woman. A 27-yr-old woman presented with abdominal pain, subsequently recognized to be caused by a right ovarian mass undergoing torsion. Following operative management, microscopic examination of the salpingo-oophorectomy specimen showed endometriosis and a predominantly cystic ovarian neoplasm with 2 distinct phenotypic areas: (1) a yolk sac tumor component containing Schiller-Duval bodies and (2) a low-grade endometrioid carcinoma component with squamous metaplasia. Immunohistochemical evaluation showed distinct profiles in the yolk sac tumor (estrogen receptor/progesterone receptor/PAX8 negative, SALL4/Glypican 3 positive) and endometrioid (estrogen receptor/progesterone receptor/PAX8 positive, SALL4/Glypican 3 negative) components. Given these findings, the diagnosis of an endometriosis-associated endometrioid adenocarcinoma with a somatically derived yolk sac tumor was rendered. The tumor was staged as pT1c1 due to intraoperative spillage. The patient underwent chemotherapeutic treatment and after 15 mo of follow-up, she was alive with no evidence of recurrence. This example demonstrates that somatic yolk sac tumor differentiation in ovarian epithelial neoplasia can occur in young patients; awareness of this phenomenon is important as somatic and germ cell yolk sac neoplasia have different behavior and therapy.