An Uncommon Gastric Submucosal Tumor With Mucosal Erosion

Abstract

A 54-year-old man with no prior medical history was referred to our hospital for a gastric lesion. An upper endoscopy showed a subepithelial tumor with a central erosion measuring 35 mm in size, located on the posterior wall of the gastric body (Figure A). Biopsy specimens from the depressed and elevated areas showed no neoplastic changes. Endoscopic ultrasonography showed a multicystic heterogeneous component (Figure B). Contrast-enhanced computed tomography showed that some of the cystic components showed contrast (Figure C). T2-weighted magnetic resonance imaging (MRI) also showed multicystic and heterogeneous tissue, and T1-weighted contrast-enhanced MRI showed cystic wall enhancement in the tumor. We successfully performed en bloc resection of the tumor using endoscopic submucosal dissection. The patient was discharged without complication. Histologically, dilated pseudopyloric glands and smooth muscle proliferation were observed in the submucosal layer with inverted and expansive growth (Figure D). Immunohistochemical analysis indicated that those glands were Mucin (MUC)10 and MUC2 negative, and MUC5AC and MUC6 positive. The mucosal layer was defective at the center of the lesion. The horizontal and vertical margins were negative. There was no sign of atypia. The pathologic diagnosis was a gastric hamartomatous inverted polyp (GHIP). GHIPs are rare gastric polyps that account for less than 1% of all gastric tumors.1Iida M. Yao T. Watanabe H. et al.Fundic gland polyposis in patients without familial adenomatosis coli: its incidence and clinical features.Gastroenterology. 1984; 86: 1437-1442Abstract Full Text PDF PubMed Scopus (63) Google Scholar There have been few reports of endoscopic submucosal dissection of GHIP,2Odashima M. Otaka M. Nanjo H. et al.Hamartomatous inverted polyp successfully treated by endoscopic submucosal dissection.Intern Med. 2008; 47: 259-262Crossref PubMed Scopus (22) Google Scholar and this case includes MRI findings. Although GHIP can mimic gastric intestinal stromal tumors,3Mori H. Kobara H. Tsushimi T. et al.Two rare gastric hamartomatous inverted polyp cases suggest the pathogenesis of growth.World J Gastroenterol. 2014; 20: 5918-5923Crossref PubMed Scopus (9) Google Scholar such as in this case, the findings of endoscopic ultrasound, computed tomography, and MRI are relatively specific. The possibility of GHIP should be considered in the differential diagnosis of gastric submucosal tumors because this can help direct therapeutic decisions. GHIP may have a potential risk of malignancy.4Oh S.J. Oh C.A. Kim D.H. et al.Adenocarcinoma derived from gastric hamartomatous polyps.J Korean Surg Soc. 2011; 81: 419-422Crossref PubMed Scopus (9) Google Scholar Although there has been no report of recurrence to our knowledge, annual surveillance has been performed.