Extragonadal mixed germ cell tumor presenting as large mass in the pelvic cavity

Extragonadal germ cell tumors are relatively rare tumor, which usually occurs in the mediastinum or retroperitoneum. In this report, we present a case of primary mixed germ cell tumor (GCT) arising in the pelvic cavity. A 38-year-old male with acute abdominal pain was admitted to our hospital. Computed tomography scan imaging demonstrated a large mass in the pelvic cavity. Histological examination of the specimen revealed germ cell tumor with dual morphology. Immunohistochemical studies detected placental alkaline phosphatase (ALP), OCT3/4, ALP, and pancytokeratin. Taking these results together with the patient's other clinical manifestations, this case was diagnosed with mixed GCT, i.e., seminoma plus yolk sac tumor. Chemotherapy was successful. Mixed germ cell tumor in the pelvic cavity is extremely rare but should be considered as a cause of pelvic mass formation.