ABSTRACT
Neuroendocrine cells are distributed throughout the body and they are found in the gastrointestinal tract, pancreas, lung, thyroid, adrenal gland and many other organs, and especially the gastrointestinal tract. As a consequence, neuroendocrine tumors of the colon and rectum are common neoplasm. Several cases of the benign carcinoid tumor and a few cases of the malignant carcinoid tumor of the colon and rectum have been reported. Yet there have been no reports on concurrent malignant carcinoid tumor and benign carcinoid tumor at the same site of the colon. A 60-year-old man presented with an asymptomatic rectal mass. After the mass was evaluated and operated on, it was confirmed to be a concurrent malignant carcinoid tumor and benign carcinoid tumor of the rectum, and metastasis to the liver was also found.