A pediculed tumor of the rectum was discovered in a 63 years old man. Within the tumor adenomatous dysplastic proliferation was associated with a neuroendocrine small-cell anaplastic carcinoma. The neuroendocrine nature of the tumor was suspected on conventional optic microscopy and confirmed by a positive Grimelius technique. Specific typical granules were also found on electron microscopy. Immunohistochemical techniques using neurospecific enolase were also positive. Carcinomatous invasion was limited to the submucosa, but the surgical specimen showed that one lymph node was metastatic. Three months later, hepatic metastasis was suspected on physical examination and the patient died of hepatic failure ten months after the discovery of the tumor. Twenty-two similar cases were found in the literature: of these five cases were associated with benign adenomatous lesions. In all cases the patients died of early metastatic diffusion. This tumor raises the problems of diagnosis, terminology, classification and therapy: only aggressive chemotherapy, similar to that applied to the same type of carcinoma in the respiratory tract might improve prognosis.