Poorly differentiated squamous cell carcinoma: the smears show many anaplastic large cells, and our somewhat misleading diagnosis was anaplastic tumor of uncertain histogenesis, we favor sarcoma. The H&E slides showed also an anaplastic large cell tumor with areas of squamous cell carcinoma. Immunohistochemical studies confirmed the epithelial nature of the tumor. This case illustrates the difficult differential diagnosis of poorly differentiated lung tumors.