Primary choriocarcinoma of the lung.

A case of primary choriocarcinoma of the lung in a postmenopausal woman is described and the literature is reviewed. To our knowledge, this is the first report in the English-language literature of pulmonary choriocarcinoma documented by immunoperoxidase staining for human chorionic gonadotropin, and shown to be primary in the lung by a thorough autopsy. Extragonadal, nongestational choriocarcinoma rarely occurs in the lung; less than 15 cases interpreted as primary pulmonary choriocarcinoma have been reported. This tumor exemplifies expression of a fetal gene in a malignancy of somatic cell origin. We propose that primary pulmonary choriocarcinoma arises from epithelial cells which may undergo metaplasia or divergent differentiation. Such differentiation may occur in visceral carcinomas as a focal change, and rarely as the sole pathway of tumor differentiation in extragonadal organs, where it has been termed primary choriocarcinoma or giant cell carcinoma with ectopic human chorionic gonadotropin production.