Primary endodermal sinus tumor of the omentum.

Endodermal sinus tumor (EST) is a rare neoplasm which usually arises in the testis or ovary. But extragonadal EST is well recognized and may arise in a wide array of sites such as the mediastinum, vagina, and brain. We report a case of primary EST of the omentum and to our knowledge it is the first case of omental EST in the literature. A 45-year-old woman with a history of abdominal distension was treated with total abdominal hysterectomy with bilateral salpingo-oophorectomy and infracolic omentectomy, followed by four cycles of BEP (bleomycin, etoposide, cisplatin) combination chemotherapy. Microscopically, the tumor exhibited typical patterns of EST and stained for alpha-fetoprotein and cytokeratin. She has remained free of disease for 10 months of follow-up. According to previous studies, debulking surgery and BEP chemotherapy were used as primary therapy with good results. The subject of extragonadal EST is reviewed, and the possible histogenesis of this tumor at such a rare site is discussed.