Primary gastric choriocarcinoma. Report of an autopsy case with immunohistochemical study.

An autopsy case of primary gastric choriocarcinoma of a 70-year-old Japanese female is presented. The tumor was initially diagnosed as poorly differentiated adenocarcinoma of the stomach by biopsy. Autopsy revealed co-existence of choriocarcinoma and adenocarcinoma in the stomach and a large amount of human chorionic gonadotropin in the serum. The choriocarcinoma metastasized to the liver, lung, and omentum, and the adenocarcinoma to lymph nodes. In the gastric tumor, immunohistochemical stains showed human chorionic gonadotropin in choriocarcinoma cells, alpha-fetoprotein and carcinoembryonic antigen in adenocarcinoma cells. The pathogenesis and pathological characteristics of primary gastric choriocarcinoma are discussed.