A white opaque substance-positive gastric hyperplastic polyp with dysplasia.

The endoscopic findings of gastric hyperplastic polyps (HPs) with dysplasia have not been well-defined, and the clinical significance of these lesions, including their malignant potential, is unclear. In this report, we describe a case of a white opaque substance (WOS)-positive gastric HP with dysplasia. A 76-year-old woman was referred to our hospital for endoscopic resection of a gastric HP. Upper endoscopy revealed a 25-mm whitish and reddish polypoid lesion on the greater curvature in the lower third of the stomach. The whitish part was diagnosed as a WOS using conventional and magnifying endoscopy with narrow band imaging. An examination of the biopsy specimen indicated that the lesion was a typical gastric HP. However, because of its color and the presence of a WOS, we suspected that this lesion was an atypical gastric HP. Therefore, we performed a polypectomy. Histopathologically, diffuse low- to high-grade dysplasia was found on the surface of the polyp. We performed immunohistochemical staining using a monoclonal antibody specific for adipophilin as a marker of lipid droplets (LDs). LDs were detected in approximately all of the neoplastic cells, especially in the surface epithelium of the intervening apical parts and were located in the subnuclear cytoplasm of the neoplastic cells. According to endoscopic and histopathological findings, the WOS-positive epithelium indicated dysplasia of the gastrointestinal phenotype, which could absorb lipids. The presence of a WOS in a gastric HP may be considered an endoscopic finding that is predictive of the neoplastic transformation of a gastric HP. We suggest that a WOS-positive gastric HP should be resected endoscopically to investigate its neoplastic transformation.