Primary Yolk Sac Tumor of the Endometrium: A Case Report and Comprehensive Literature Review

Yolk sac tumor (YST) of the endometrium is very rare, with fewer than 40 cases reported in the English literature. We here describe a case of primary endometrial YST and discuss the clinicopathological features with a literature review. A 66-year-old Chinese woman presented with abnormal vaginal bleeding for 15 days and a uterine mass for 3 days. The preoperative alpha-fetoprotein (AFP) level was 9652.0 ng/mL, while other serum tumor markers, including carcinoembryonic antigen (CEA), neuron-specific enolase (NSE), and β-human chorionic gonadotropin (β-HCG), were 40.2 ng/mL, 29.19 ng/mL, and 27.7 mIU/mL, respectively. Pelvic ultrasound imaging revealed a 7.1 × 6.6 × 6.0 cm mass in the endometrial cavity. The patient underwent total abdominal hysterectomy, salpingo-oophorectomy, and partial omental resection. The morphologic and immunohistochemical pattern (cytokeratin+++, Sal-Like Protein 4+++, AFP++, Focal Hepatocyte Nuclear Factor 1 beta+, and Focal Glypican-3+) was consistent with a primary YST of the endometrium, and the final pathologic stage was IVb based on the International Federation of Gynecology and Obstetrics (FIGO) staging. Postoperative serum AFP level was 5193.0 ng/mL 5 days after the operation. Primary endometrial YST is extremely rare. It should be differentially diagnosed from other uterine malignancies. Complete surgical staging combined with chemotherapy may have a better survival impact on endometrial YST.