An autopsy case of primary gastric choriocarcinoma.

An autopsy case of primary gastric choriocarcinoma in a 55-year-old male is presented. The tumor was diagnosed as choriocarcinoma of the stomach from a histological examination of biopsy specimens. The level of human chorionic gonadotropin (HCG) was significantly increased in the serum and urine. A histological examination of autopsy specimens showed the tumor of the stomach to be a pure choriocarcinoma composed of syncytiotrophoblasts and cytotrophoblasts with a mixture of eosinophilic necrotic tissues, but with no elements of adenocarcinoma. The tumor showed metastases and/or invasions to the liver, lungs, pancreas, omentum, pleura, peritoneum and lymph nodes. Positive immuno-histochemical staining for the beta-subunit of HCG (HCG-beta) in the gastric tumor was demonstrated in the form of granular diffuse deposits in the cytoplasm of trophoblasts and predominated in syncytiotrophoblasts over transitional cells. Under electron microscopic observation, positive immunostaining for HCG-beta was observed in the perinuclear space, cisternae of the rough endoplasmic reticulum (RER) and secretory vesicles of syncytiotrophoblasts and transitional cells.