Gastric carcinoids.

Gastric carcinoids are classified into three types mostly on the basis of their pathological associations: 1) type I, associated with atrophic corporal gastritis; 2) types II, associated with Multiple Endocrine Neoplasia type 1; 3) type III, sporadic. Type I and II carcinoids develop through a histologically recognizable sequence: hyperplasia-dysplasia-neoplasia. Their pathogenesis depends on the combined action of promoting agents, mostly hypergastrinaemia, and of transforming agents, the role of which is currently under investigation. Their prognosis is generally favourable. In contrast, type III tumours are often malignant and their pathogenesis has not been clarified yet.