Choriocarcinoma involving the pancreas as first manifestation of a metastatic regressing mixed testicular germ cell tumor.

We describe an unusual case of metastatic choriocarcinoma of the pancreas arising from a regressing testicular mixed germ cell tumor that clinically mimicked a primary pancreatic tumor. A 54-year-old male presented with a 2-month history of progressive upper abdominal pain, weight loss, and jaundice. He also had a history of recurrent epididymitis associated with the presence of a right testicular mass shown to be cystic by ultrasound and stable for at least 10 years. A computed tomography scan showed an isolated 6 cm mass in the head of the pancreas. A pancreaticoduodenectomy was performed. Upon histological examination, the pancreatic tumor showed extensive hemorrhage and necrosis. In the viable area, the tumor was composed of an intimate mixture of mononuclear cytotrophoblast cells and multinucleated syncytiotrophoblasts with vascular invasion. These characteristic features led to the correct diagnosis on frozen section. The cytology of the tumor was nonspecific and suggested undifferentiated carcinoma of the pancreas. The trophoblastic origin of the tumor cells was confirmed by immunohistochemistry staining. The testicular mass showed a regressed mixed germ cell tumor of predominantly seminoma with focal teratoma but without a choriocarcinoma component. In conclusion, we present a rare and unusual case of a regressing testicular mixed germ cell tumor that presented as a primary pancreatic tumor. Cytological features of the pancreatic mass were not specific and raised the possibility of a primary undifferentiated carcinoma of the pancreas. Characteristic histological features of choriocarcinoma led to the correct diagnosis on frozen section. Subsequent resection of the testicular mass confirmed the presence of a cystic and scarring (regressing) mixed germ cell tumor but without evidence of choriocarcinoma.