Primary choriocarcinoma of the lung: case report of two male subjects.

Extragenital choriocarcinoma in the male is known to occur in retroperitoneum, mediastinum and pineal body in a high proportion, and there have been no certain reports of lung origin. We studied two cases of choriocarcinoma arising from the lung in the male by histological, electronmicroscopical, immunofluorescent, and immunoenzyme methods. Histologically, characteristic changes of choriocarcinoma, composed of irregular complex of cytotrophoblasts and syncytiotrophoblasts with massive necrosis and hemorrhage were demonstrated. These two cell patterns, characteristic of choriocarcinoma, were also demonstrated electronmicroscopically and differed from giant cell carcinoma of the lung. By immunofluorescent and immunoenzyme methods, anti-HCG reactive particles were seen in the cytoplasm mainly of syncytiotrophoblasts and proved HCG production function of the tumor.