Original ArticlesGastric Inverted Polyps—Distinctive Subepithelial Lesions of the Stomach Clinicopathologic Analysis of 12 Cases With an Emphasis on Neoplastic PotentialKim, Ji-Ye MD*; Ahn, Soomin MD†; Kim, Kyoung-Mee MD†; Chang, Sun Hee MD*; Kim, Han Seong MD*; Lee, Jun Haeng MD‡; Kim, Jae J. MD‡; Sohn, Tae Sung MD§; Kang, Hye Ju MD∥; Joo, Mee MD, PhD* Author Information *Department of Pathology, Ilsan Paik Hospital, Inje University College of Medicine ∥Department of Pathology, National Cancer Center, Goyang Departments of †Pathology and Translational Genomics ‡Medicine §Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea J-.Y.K. and S.A. contributed equally. Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article. Correspondence: Mee Joo, MD, PhD, Department of Pathology, Ilsan Paik Hospital, Inje University College of Medicine, 170 Juhwa-ro, Ilsanseo-gu, Goyang 10380, South Korea (e-mail: [email protected]). The American Journal of Surgical Pathology: May 2021 - Volume 45 - Issue 5 - p 680-689 doi: 10.1097/PAS.0000000000001651 Buy Metrics Abstract Gastric inverted polyps (GIPs) are rare gastric polyps characterized by a submucosal inverted growth of mucosal components. Because of their rarity, they are not well characterized and are diagnostically challenging. We examined 12 cases of GIPs arising in 8 male and 4 female patients (mean age: 56 y). Most GIPs (11/12, 92%) occurred as a single, rounded subepithelial lesion in the body or fundus (mean size: 14.9 mm). Histologically, GIPs consisted of gastric-type glandular epithelium and smooth muscle component, growing in an endophytic manner; however, they displayed significant morphologic variations. We classified GIPs into 3 subtypes by the following features: communication with the mucosal surface, smooth muscle boundary, and tissue organization. The defining characteristics of type 1 were a mucosal communicating structure at the center and a well-defined smooth muscle boundary, resulting in a characteristic low-magnification morphology of a round vase. Type 2 had an organized glandular proliferation with smooth muscle boundary and no central communicating structure. Type 3 GIPs had no mucosal communicating structure or smooth muscle boundary; its key histologic feature was the lobular organization pattern produced by proliferations of cystic or hyperplastic glands and smooth muscle. All type 1 GIPs exhibited coexisting adenocarcinoma (3 cases) or stromal proliferation (3 cases). Three patients with type 2 GIP had separate adenocarcinoma. None of the type 3 GIPs had accompanying carcinoma. In conclusion, GIPs are a heterogenous group showing different morphology and clinical behavior. Notably, type 1 GIP could be considered a precancerous lesion with the potential to develop adenocarcinoma. Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.