[High-grade Fetal Lung Adenocarcinoma with Hepatoid Adenocarcinoma Component].

A 71-year-old man with a history of smoking 1 pack of cigarettes per day for the past 53 years visited our department with chest pain, and was diagnosed as spontaneous pneumothorax. A chest computed tomography scan revealed a nodular shadow in the upper portion of the left lobe of the lung, which was found to be adenocarcinoma by transbronchial lung biopsy. A left upper lobectomy and lymphadenectomy were performed. The pathological diagnosis was a high-grade fetal lung adenocarcinoma (H-FLAC) with a hepatoid adenocarcinoma component (pT2aN0M0, pStage I B). H-FLAC comprises at least 50% fetal lung-like cells, while hepatoid adenocarcinoma comprises hepatocellular carcinoma-like cells. Following the diagnosis, adjuvant chemotherapy with uracil-tegafur was started. Although both these neoplasms are known to have a poor prognosis, no recurrences were observed at 11 months postsurgery.