A gastric hamartomatous inverted polyp mimicking submucosal tumor

A 68-year-old healthy woman was referred for endoscopic screening in the course of her annual medical check-up. Gastroscopy revealed a 4 × 2 cm protruding lesion with red colored smooth surfaced mucosa accompanied by slight center depression on the greater curvature side of the middle gastric body (Fig. A). Endoscopic ultrasonography disclosed a homogeneous hypoechoic tumor, with a smooth margin, originating from the gastric muscularis propria (Fig. B). Submucosal tumors of the stomach are considered benign. However, they have the potential for malignant transformation, especially if they originate from the muscularis propria layer. Therefore, endoscopic full-thickness resection was performed to remove it. Unexpectedly, the lesion was histologically characterized by submucosal growth of hypertrophic glands with focal cystic dilatation, accompanied by smooth muscle proliferation and inflammatory cell infiltration in the stroma (Fig. C). The diagnosis was consistent with gastric hamartomatous inverted polyp.