Clinicopathological Characteristics and Endoscopic Diagnosis of Colorectal Neuroendocrine Tumor

Abstract

In Japan, colorectal neuroendocrine tumors (NET) most commonly arise in the rectum, particularly the lower portion. Many lesions are asymptomatic and detected when they are 10 mm or less in diameter. Endoscopic examination typically shows a yellowish, submucosal tumor, often with dilated blood vessels on its surface. Endoscopic ultrasonography is useful for evaluating the depth of invasion. In a rectal NET, the macroscopic type and size of the tumor are closely related to the depth of invasion and the risk of metastasis to lymph nodes. In particular, when the pedunculated macroscopic type, central depression, or tumor diameter is 10 mm or more, the risk of invasion to the proper muscle layer and metastasis increases, so caution is required. Regarding the prognosis, it has been reported that colon NET is worse than rectal NET, but it is necessary to examine many cases in the future.