Endoscopic features, pathological correlates and possible origin of foveolar gastric metaplasia presenting as a duodenal polyp.

It has recently been shown that duodenal foveolar gastric metaplasia (FGM) sometimes presents as a polyp. The mechanism by which FGM develops into a polypoid lesion is unknown and it is unclear whether this form of FGM is indistinguishable from other polypoid lesions or whether endoscopists do not recognize it because they are unfamiliar with it. We identified and retrieved archival cases of FGM endoscopically suspicious for adenomatous polyp and examined their pathological, clinical and endoscopic features. Endoscopic features of the 13 identified FGMs presenting as polyps were heterogeneous and overlapping with those of adenomatous polyps. FGM was frequently associated with mucosal and submucosal Brunner's glands, but defining and recognizing hyperplasia of these glands remains difficult. Other pathological features could not explain the development of a polypoid lesion. The endoscopic features of FGM polyps are non-specific, overlapping with those of adenomatous polyps. FGM polyps probably acquire their polypoid aspect due to association with Brunner's gland hyperplasia (BGH), which also arises due to chronic inflammation and damage. Because BGH is ill-defined and difficult to recognize, while FGM is diagnosed easily, this type of polypoid lesions has until now only been recognized based on the presence of FGM, although FGM is most likely a secondary phenomenon and not the primary cause of the polyp.