The first group is divided into three distinct subtypes: type 1: gastrin-dependent type of carcinoid accompanied by chronic atrophic gastritis complicated with hypergastrinemia and G cell hyperplasia; type 2: associated with hypertrophic gastropathy and hypergastrinemia due to MEN1/ZES; and type 3: sporadic carcinoid [102]. This evidence concerns the gene GAST and Zollinger-Ellison syndrome.