[Neuroendocrine colorectal tumors. Surgical and endoscopic treatment]

The incidence of colorectal neuroendocrine tumors (NETs) is rising in developed countries primarily as a result of increased incidental detection by endoscopy and probably also due to a more adequate diagnosis according to the WHO classification. Less than 1% of colorectal NETs produce serotonin so that such tumors are practically never associated with a hormonal carcinoid syndrome. An exact clinico-pathological staging is of paramount importance for the therapeutic strategy and comprises the classification of the tumor type (well or poorly differentiated) and the assessment of established prognostic risk factors (depth of infiltration, vascular invasion, lymph node and distant metastases). Poorly differentiated colorectal NETs often present in an advanced, metastatic state, where surgical therapy is basically palliative. Well-differentiated tumors larger than 2 cm have a high risk of metastatic spread and should be treated as adenocarcinomas by radical oncological surgical resection. This applies to the majority of colon NETs. Tumors smaller than 1 cm, mainly locacted in the rectum, only rarely metastasize and are usually accessible for endoscopic treatment or transanal local surgery. Tumors between 1 and 2 cm in size have an uncertain prognosis and additional risk factors and co-morbidities of the patient have to be considered for a suitable, multidisciplinary therapeutic decision.