Malignant transformation of foveolar hyperplastic polyp of the stomach: a histopathological study.

The author investigated histopathology of malignant changes of gastric foveolar hyperplastic polyps (GFHP). A total of 497 GFHP from 412 patients were retrospectively examined. Malignant changes were present in 11 GHP (2.2%). They were focal malignancies and well-differentiated adenocarcinoma without apparent invasion. In all the 11 GFHP, dysplastic glands were present in the vicinity of carcinomatous foci. Focal intestinal metaplasia was recognized in one case and was absent in the remaining 10 GFHP. Focal dysplastic glands were recognized in 51 GFHP (10%). Of these, four GFHP were associated with focal intestinal metaplasia, but the remaining 47 GFHP were not associated with intestinal metaplasia. Intestinal metaplasia alone was recognized in 23 GFHP (5%). Immunohistochemically, all carcinomatous foci within the 11 GFHP with malignant transformation showed positive p53 expression and high Ki-67 labeling. Of the 51 GFHP with dysplasia, 42 GFHP were positive for p53 protein, and the remaining 9 GFHP were negative for p53 protein. The dysplastic lesions of the 51 GFHP showed relatively high Ki-67 index. Intestinal metaplasia within GFHP was negative for p53 protein and showed low Ki-67 labeling. These results suggest that malignant transformation of GFHP may occur in 2.2% of cases, and that malignant changes develop via hyperplasia-dysplasia-carcinoma sequence in GFHP. Intestinal metaplasia within GFHP was not associated with carcinogenesis of GFHP.