Small, polypoid-appearing carcinoid tumors of the rectum: clinicopathologic study of 16 cases and effectiveness of endoscopic treatment.

Fifteen cases of small-size rectal carcinoid tumors (RCTs) were discovered among a total of 21,522 healthy teachers who received proctosigmoidoscopy. Adding another case seen in the outpatients, a total of 16 RCTs were clinicopathologically studied. The average age of the patients was 48.8 yr, and the incidence was predominantly among males. Prior to endoscopy, digital examination of the rectum revealed a palpable firm nodule in 13 patients. On endoscopy, RCTs were generally round, yellow-discolored polyps with a size less than 13 mm in diameter, covered by a normal-appearing mucosa. An erythematous change or depression was seen in three tumors. Histologically, they showed pure insular, trabecular, or mixed structures, and tumor cells were confined to the mucosa and/or submucosa in all cases. Immunohistochemically, RCTs never failed to show focal or diffuse positivities for chromogranin A and/or neuron-specific enolase. Pancreatic polypeptide was immunostained in 14 tumors to a varying degree. The tumors having been safely treated by endoscopic polypectomy and/or surgical excision, all of the patients are alive and clinically free of disease during the average observation period of 79 months.