[Carcinoid tumor of the rectum: report of a case with histochemical and ultrastructural study]

A case of rectal carcinoid tumor in a 54 year old female patient is reported. An endoscopic resection of an elevated high rectal lesion was done after performed a well established radiologic and endoscopic diagnosis. The tumor was localized in the submucosa of the rectum. Microscopically, neoplastic cells were mainly arranged in nests and trabecular structures within thin fibrous stroma. Mitotic figures and pleomorphism cellular were uncommon. Histochemically the argyrophil stain of Grimelius were positive but the Masson-Fontana silver stain were negative. At the ultrastructural level neurosecretory granules were found in the cytoplasma, varied in shape and size, and 150-400 nm in longest axis.