Neuroendocrine tumors of the stomach

The diagnosis and therapy of neuroendocrine tumors (NETs) of the stomach are based on their exact classification and risk stratification. Since the incidence of gastric NETs has risen sharply over the last 35 years and most tumors are detected endoscopically at an early stage, they have come to represent a challenge for the pathologist. Gastric NETs are classified according to the WHO and TNM classifications and additionally separated into four biologically distinct types: Well differentiated type 1 and 2 gastric NETs (G1) smaller than 2 cm, and type 3 smaller than 1 cm that do not infiltrate the muscularis propria or show angioinvasion have a good prognosis and can be removed endoscopically. Well differentiated type 1 and 2 gastric NETs (G1-G2) larger than 2 cm or type 3 with a diameter above 1 cm or with infiltration of the muscular wall and/or angioinvasion and poorly differentiated (type 4) neuroendocrine carcinomas carry a poor prognosis and need to be treated aggressively. Endosonography is the method of choice for determining the size, depth of infiltration and presence of lymph node metastases. With exact diagnosis and adequate treatment, the majority of patients with gastric NETs have a favorable prognosis.