Colonic adenocarcinoma with numerous paneth and endocrine cells.

Numerous granular eosinophilic cells corresponding to Paneth cells were unexpectedly revealed in a moderately differentiated adenocarcinoma of the hepatic flexure of the colon in a 76-year-old man. These cells were clearly seen in routine slides and their nature was confirmed by Masson's trichrome stain, by immunohistochemical reaction for lysozyme, and by electron microscopy. The tumor contained also cells intermediate between Paneth and goblet cells (with both supranuclear granules and mucous globules), observed in Masson's trichrome stain and in electron microscope. Additionally, immunohistochemical reaction for chromogranin A was performed and irregularly scattered neoplastic endocrine cells were visualized in the tumor. The light microscopic and ultrastructural features of this rare neoplasm are described together with detailed clinical data. The incidence and significance of the Paneth cell and endocrine differentiation in colorectal carcinomas are discussed with the review of the literature.