Mucus-secreting carcinoid tumor in a colonic diverticulum: report of a case.

A mucus-secreting carcinoid tumor arising in a colonic (rectosigmoid) diverticulum is presented. Carcinoid tumors in colonic diverticula have not been previously reported. The presence of mucin and argentaffin granules in the same tumor cell is illustrated. The recognition of mucus-secreting carcinoid tumors is emphasized in order to avoid overtreatment of small colonic carcinoid tumors by extensive surgical procedures.