The authors retrospectively reviewed data regarding 14 patients with sarcomatoid carcinomas of the lung seen and treated at M.D. Anderson Cancer Center from 1955 to 1986. The following were the histologic criteria for inclusion in the study: (1) the concurrent presence of malignant epithelial and sarcomatoid spindle cell components, and (2) positive immunoreactivity for antikeratin antibody or ultrastructural demonstration of epithelial differentiation in sarcomatoid tumors in which the epithelial component was inconspicuous. For the sarcomatoid components, the most frequent pattern was malignant fibrous histiocytoma, which was present in ten tumors. An unclassified sarcomatoid pattern was found in two cases and a fibrosarcomatous pattern in two remaining cases. Clinically, the median patient age was 59 years; 12 patients were male and 2 were female; 13 were smokers and 1 used snuff. Three patients had Stage I, ten had Stage III, and one had Stage IV disease. One patient with Stage I, seven with Stage III, and one with Stage IV disease died of their carcinomas 2 to 26 months after diagnosis (median survival time 12 months). All patients who had lymph node metastases at presentation died of disease. The authors concluded the following: (1) patients with sarcomatoid carcinoma of the lung usually presented at an advanced stage; (2) lymph node metastasis, as with a usual carcinoma of the lung, is an important prognostic factor; and (3) for all lung tumors with a sarcomatoid pattern, especially a malignant fibrous histiocytoma pattern, extensive samples should be obtained and immunoperoxidase or ultrastructural studies done to identify epithelial differentiation.