Pulmonary sarcomatoid carcinoma is rare, with limited treatment options and poor prognosis. In contrast to other non small cell lung carcinomas, not much is known about its molecular biology. In an endemic country like India, lung cancer is often masked by tuberculosis and presents in advanced stages. We report here an unusual case of pulmonary sarcomatoid carcinoma, in a young non-smoker male, who had co-existent tuberculosis masking and delaying the diagnosis of malignancy. On molecular study, the tumor showed ALK gene rearrangement, both by immunohistochemistry and fluorescence in-situ hybridization, which has been reported only twice previously. Presence of ALK gene rearrangements in sarcomatoid carcinoma has significant therapeutic implications and potential for altering the prognosis of this fatal disease. Hence we recommend performing ALK gene rearrangement analysis in all cases of sarcomatoid lung carcinomas. The report discusses the diagnostic approach and provides insight into the molecular pathogenesis of this exceedingly rare malignancy.