A Case of Giant Cell Carcinoma of the Lung with a Component of Well Differentiated Adenocarcinoma

A 70-year-old man was referred to our hospital for evaluation of a cavitary lesion in the left lung. Chest CT showed a mass lesion with a cavity, 17×12mm in size, in the peripheral region of left S1+2a. On thoracotomy giant cell carcinoma was diagnosed by frozen section, and left upper lobectomy was performed. Themaximum diameter of the resected tumor was 18 mm and no metastatic lymph node was detected, therefore this was an early peripheral lung cancer. This tumor was partly composed of well differentiated adenocarcinoma and electron microscopically, the giant cells had microvilli. An immunohistochemical comparison of the labelling indices of p53 protein and MIB-1 antibody among tumor components showed those of the giant cell carcinoma area to be higher than those of the adenocarcinoma area. This giant cell carcinoma may have been transformed by a dedifferentiation of an adenocarcinoma.