Gastric Inverted Polyps—Distinctive Subepithelial Lesions of the Stomach

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.

Gastric hamartomatous inverted polyp: Report of three cases with a review of the endoscopic and clinicopathological features

“…27 The most frequent subtype was type 1 (6/12 patients),followed by type 2 (4 patients),and type 3 (2 patients). 27 The characteristic feature of type 1 GHIP may represent the endoscopic feature of an opening in the center to the surface with mucus outflow, which is an occasional finding of GHIPs (15 tumors). According to this classification, two tumors of the present series were classified as type 2 (Patients 2 and 3) because no communication between the submucosal lesion and the surface mucosa was noted, whereas the remaining tumor was classified as type 3 (Patient 1).…”

“…As described above, differentiating GHIPS from other SMTs of the stomach, including those of the submucosal heterotopic gastric mucosa and gastritis cystica profunda, might be difficult 27 ; thus, additional clinicopathological studies are needed to clarify the classification of the SMTs of the stomach. Of importance, three of six patients with a type 1 GHIP were shown to coexist with an adenocarcinoma within the lesion of a GHIP, and a hyperplasia–dysplasia–carcinoma sequence was also observed within the lesion 27 . Thus, a type 1 GHIP may have malignant potential, and the reason for this may be that the central communicating structure allowed a continuous exposure of luminal carcinogen and mechanical stress to the submucosal glandular cells of a GHIP 27 .…”

“…27 Thus, a type 1 GHIP may have malignant potential, and the reason for this may be that the central communicating structure allowed a continuous exposure of luminal carcinogen and mechanical stress to the submucosal glandular cells of a GHIP. 27 The present study consisted of type 2 and type 3 GHIPs, and no carcinomatous component was noted within the lesion. Moreover, gene analysis demonstrated no significant mutations in any of the three tumors.…”

“…Type 1 characteristically has a communicating structure with an overlying mucosa and a well‐defined smooth muscle boundary showing a normal gastric mucosal architecture (a hyperplastic foveolar epithelium at the center of the submucosal cysts and pyloric or fundic glands at the periphery). Type 2 is characterized by an isolated submucosal lesion surrounded by smooth muscle bundles with no central communicating structure, and type 3 is characterized by no mucosal communication or smooth muscle boundary and a significantly distorted tissue organization 27 . The most frequent subtype was type 1 (6/12 patients), followed by type 2 (4 patients), and type 3 (2 patients) 27 .…”

“…Of importance, three of six patients with a type 1 GHIP were shown to coexist with an adenocarcinoma within the lesion of a GHIP, and a hyperplasia-dysplasia-carcinoma sequence was also observed within the lesion. 27 Thus, a type 1 GHIP may have malignant potential, and the reason for this may be that the central communicating structure allowed a continuous exposure of luminal carcinogen and mechanical stress to the submucosal glandular cells of a GHIP. 27 The present study consisted of type 2 and type 3 GHIPs, and no carcinomatous component was noted within the lesion.…”