Polypoid carcinoma of the esophagus is a rare variant of squamous carcinoma, which occurs typically in elderly patients who present with symptoms of dysphagia. This tumor has been given a variety of names, including spindle cell carcinoma, carcinosarcoma, and pseudosarcoma. These designations reflect the controversy surrounding the nature of the spindle cell component of this lesion. We have studied a case of polypoid carcinoma of the esophagus with immunoperoxidase staining for keratin which has been shown to be specific for epithelial cells. Positive staining for keratin was demonstrated in both the carcinomatous and spindle cell "sarcomatous" appearing components of the tumor, supporting the contention that this tumor is of entirely epithelial origin.