Combined choriocarcinoma and adenocarcinoma of the lung

Combined choriocarcinoma and adenocarcinoma in the lung of a 71-year-old Japanese male is reported. In the upper lobe of the right lung (S1 + 2), a choriocarcinoma coexisted with an adenocarcinoma, but distinct metastatic lesions were noticed separately in the lungs, kidney, bone marrow and lymph nodes. Although immunohistochemical examination revealed intensely positive reactivity with anti-human chorionic gonadotropin (HCG) in trophoblastic cells, weak immunoreactivities were also observed in a few cells with anti-human placental lactogen (HPL), anti-pregnancy-specific beta glycoprotein (SPI), anti-epithelial membrane antigen (EMA), anti-carcinoembryonic antigen (CEA), anti-cytokeratin (keratin) and KM-93 (lung adenocarcinoma-associated antibody). In the adenocarcinoma, the tumor cells were positively stained for CEA, EMA, keratin and KM-93, but there were no positive reactivities for HCG, HPL and SPI. These findings suggest that primary choriocarcinoma of the lung may arise through dedifferentiation of adenocarcinoma.