Well-differentiated Neuroendocrine Tumor (Carcinoid)
Gastric neuroendocrine tumors come in four types. Type 1 tumors arise in chronic atrophic gastritis (autoimmune gastritis) and make up about 65% of all gastric neuroendocrine (NE) tumors. They have excellent prognosis. Type 2 tumors are associated with MEN-I syndrome and Zollinger-Ellison syndrome. They make up about 15% of gastric NE tumors. Their prognosis is intermediate between types 1 and 3. Type 3 tumors are sporadic and make up about 20% of gastric NE tumors. They show a greater propensity for invasion and metastases and have the worst prognosis. Type 4 tumors show features of glandular as well as neuroendocrine differentiation and are uncommon.