Histopathological classification and malignant change in gastric polyps.

A total of 611 gastric polyps from 275 cases were studied and were classified into four subtypes. Type I was the most common type and types II, III, and IV were less common. Type I and II, considered to be non-neoplastic polyps because of the absence of dysplasia, showed an extremely low malignant potential. Type III showed a two layer structure, the upper layer of which was composed of dysplastic epithelia. This type showed a low malignant potential despite the dysplasia. The type IV polyp showed macroscopical and histological findings similar to those of colonic adenoma. This type was considered to be truly neoplastic and to be the most important of the four subtypes because of its high malignant potential. Type III and IV should be clearly separated and treated differently.