The number of detected GEP-NET increased about 5-fold in Germany between 1976 and 2006. At the same time, their anatomic distribution changed, and the survival of GEP-NET patients improved significantly. Second malignancies are common and influence the overall survival of GEP-NET patients. Thus, GEP-NET warrant our attention as well as intensive research on their tumorigenesis.

Clinically detected neuroendocrine neoplasms of the rectum have increased 10- to 30-fold in frequency over the past 45 years in Germany. Endoscopic ultrasonography is the method of choice for exact determination of the size of the tumor, depth of infiltration and detection of local lymph node metastases. Well-differentiated neuroendocrine tumors ≤ 10.0 mm in size that do not infiltrate the muscularis propria can be endoscopically resected. In the case of lymphatic or blood vessel invasion or spread to lymph nodes, surgical lymph node dissection is indicated. The management of well-differentiated, neuroendocrine rectal tumors 10.1-20 mm in size is still a matter of debate. Old age and multimorbidity favor a conservative endoscopic approach; however, in the case of fit young patients, surgical management has to be considered. For neuroendocrine rectal neoplasms ≥ 20 mm in size, the risk of metastatic spread increases to 60-80 % indicating that an endoscopic resection is not adequate. Due to the introduction of screening colonoscopy, neuroendocrine rectal tumors are nowadays diagnosed mostly at a prognostically favorable early stage.

Neuroendocrine tumors (NETs) of the small bowels are on the rise: in the US they have increased by 300-500% in the last 35 years. At the same time their prognosis has been much improved. Most NETs of the duodenum are nowadays detected "incidentally" and therefore recognized at an early stage. Duodenal NETs that are well differentiated, not larger than 10 mm in greatest dimension and limited to the mucosa/submucosa can be endoscopically resected. In NETs with a size between 10 mm and 20 mm the therapeutic strategy has to be individually discussed. Endoscopic ultrasound is the method of choice to determine tumor size and depth of infiltration. Surgery is indicated for well differentiated duodenal NETs greater than 20 mm, for localized sporadic gastrinomas and for localized poorly differentiated NE cancers. Surgery is also indicated for localized/regional ileal NETs. Advanced ileal NETs with a carcinoid syndrome are treated with stable somatostatin analogs. This treatment also significantly improves the (progression-free) survival in patients with metastatic NETs of the ileum. For optimal NET management tumor biology, type, localization and stage of the neoplasm as well as the individual situation of the patient have to be taken into account.

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