A case of gastric hamartomatous inverted polyp (HIP) discovered unexpectedly in upper gastrointestinal endoscopy

An 88-year-old woman was admitted to our hospital with general malaise. Upper gastrointestinal endoscopy revealed a submucosal tumor-like lesion in the body of stomach. Endoscopic ultrasonography (EUS) revealed the lesion to be in the submucosal layer with multiple cyst-like masses. As definitive diagnosis was difficult from these findings and adenocarcinoma could not be ruled out, we performed partial gastrectomy. Pathological examination revealed the mucosa invaginated into the submucosal layer. Based on these findings, we diagnosed the lesion as HIP. If one is able to suspect HIP, EUS becomes useful in its diagnosis. If it can be confirmed that the lesion is localized within the submucosal layer by EUS, minimally invasive treatments such as endoscopic submucosal dissection can be selected. HIP thus should be included in the differential diagnoses of protruding lesions in order to perform appropriate and accurate pre-operative diagnoses.