Undifferentiated carcinoma of the lung with osteoclast-like giant cells.

We treated a patient with undifferentiated carcinoma of the lung, with osteoclast-like giant cells resembling those of the giant cell tumor of bone. The clinical and morphologic characteristics of this case are documented, and the literature concerning this type of tumor is reviewed. The tumor differed histologically from the pleomorphic carcinoma, which occurs most commonly in the lung, and showed diverse pleomorphic manifestation with benign looking osteoclast-like multinucleated cells and bizarre giant cells. In addition, and undifferentiated carcinoma with a sarcoma-like appearance containing small areas of papillary adenocarcinoma was evident in the tumor.