No transformation of a fundic gland polyp with dysplasia into invasive carcinoma after 14 years of follow-up in a proton pump inhibitor-treated patient: A case report

A fundic gland polyp (FGP) is a common gastric polyp. Intraepithelial neoplasia in FGPs, referred to as FGP with dysplasia, is often seen in patients with familial adenomatous polyposis (FAP). In sporadic FGPs, low-grade dysplasia (LGD) is rare, and high-grade dysplasia (HGD) or carcinoma arising from sporadic FGPs is extremely rare. Because of this rarity, the prognosis and appropriate management of these lesions have not been clarified. In the present case, a sporadic FGP with LGD did not develop into invasive carcinoma, but contained foci of HGD 14 years after diagnosis. The biopsy specimen of the polyp taken at the first esophagogastroduodenoscopy 15 years earlier was diagnosed as FGP without dysplasia. At the second histological examination, LGD was found. Because the polyp increased in size during proton pump inhibitor therapy for 14 years, endoscopic mucosal resection was performed. The pathological diagnosis of the resected specimen was FGP with HGD mixed in LGD, with no invasive carcinoma. Dysplasia in FGPs might have less malignant potential regardless of dysplasia or size.