[Diagnosis and treatment of colorectal neuroendocrine cell tumor]

Neuroendocrine cell tumors of the colon and rectum are divided into two groups: carcinoid tumors with low-grade atypia and malignancy; and endocrine cell carcinomas (ECCs) with high-grade atypia and malignancy. In Japan, most colorectal carcinoids are located in the lower rectum. With increasing tumor size, tumors invade deeper into the submucosal layer, and the lymph node metastatic ratio increases. It is important for decisions on treatment and predictions of prognoses to determine the depth of lesion invasion and extent of metastases before resection. Lesions 10mm or less in diameter with submucosal invasion can be treated with endoscopic mucosal resection or local surgical resection. For lesions greater than 10mm in diameter, radical surgery with lymphadenectomy should be performed. ECCs of the colon and rectum are aggressive. The reported incidence of this tumor represents less than 1% of all colorectal malignancies. It is important to recognize ECCs of the colon and rectum pathologically and to confirm the precise diagnosis using silver impregnation and immunohistochemical staining for neuroendocrine markers because they have been shown to have a particularly poor prognosis.