[A case of primary retroperitoneal tumor with combined histologic features of embryonal carcinoma and yolk sac tumor].

A case of a primary retroperitoneal tumor, combining two histologic features of embryonal carcinoma and a yolk sac tumor is reported. A 31-year-old male complained of severe abdominal pain and had a laparotomy following a diagnosis of acute panperitonitis. During the operation, a large retroperitoneal tumor attached to the abdominal aorta was found, accompanied with remarkable hemorrhage and necrosis. Histologically, the tumor showed immature large cells with a solid pattern, focally forming reticular, tubular and glomeruloid structures. PAS positive hyaline bodies, multinuclear giant cells and mitoses were noted in the tumor cells. Immunohistochemically, the tumor cells in the reticular pattern were positive for alpha-fetoprotein. No abnormality was found in the testes on palpation and ultrasound sonographic examination.