Extragonadal retroperitoneal endodermal sinus tumor in an eight-month-old female infant

We describe a rare case of an extragonadal retroperitoneal endodermal sinus (yolk sac) tumor in the minor pelvis. Radiologic investigation, which incl uded abdominal ultrasound and computed tomography (CT), showed a large soft tissue mass occupying the pelvic cavity. Radionuclide bone scans demonstra ted bone metastases. The serum alpha fetoprotein was elevated. Pathologic e xamination of the surgical specimen revealed extragonadal yolk sac tumor. I mmunohistochemically, the tumor was positive for a-fetoprotein and cytokera tins. After postoperative combination therapy, follow-up CT showed decreasi ng tumoral disease, while serum alpha fetoprotein returned to normal.