Primary pulmonary choriocarcinoma combined with adenocarcinoma.

An extremely rare autopsy case of primary pulmonary choriocarcinoma combined with adenocarcinomatous components in a 77-year-old Japanese man is described. The patient died of rapidly progressive respiratory dysfunction without ante-mortem diagnosis. Autopsy revealed necro-hemorrhagic areas of the primary lung tumor with a typical biphasic pattern of choriocarcinoma. Topographical analysis suggested that moderately to poorly differentiated adenocarcinoma components partially surrounded the choriocarcinomatous components. Moreover, dedifferentiated carcinomatous components were scattered next to both adenocarcinomatous and choriocarcinomatous areas, and a few cells of the dedifferentiated carcinomatous components had a similar immunoreaction to conventional adenocarcinomatous or choriocarcinomatous components, such as surfactant apoprotein A, placental alkaline phosphatase or beta-human chorionic gonadotropin. Additionally, epithelial membrane antigen-positive cytotrophoblastic cells were rarely found in choriocarcinomatous areas. The present case suggests that primary lung choriocarcinoma can occur closely related to conventional pulmonary adenocarcinoma, although collision tumor was not completely ruled out.