A primary adenocarcinoma of the nasal cavity with light microscopic, electron microscopic, and immunocytochemical features of an enteric-type carcinoma is presented. The carcinoma contained a variety of dense-core granules similar to those seen in enterochromaffin cells of different functional types. Some granules demonstrated an immunoreactivity with serotonin, cholecystokinin, gastrin, somatostatin and leu-enkephalin antibodies. It is suggested that the endocrine cells in the neoplasm belong to the non-neuroectodermal paraneurone system.