Clinicopathological features of autoimmune gastritis

Objective: To study the clinicopathological characteristics and pathologic diagnosis of autoimmune gastritis. Methods: Fourteen biopsies of autoimmune gastritis were collected from January 2018 to March 2019 at Guangdong Provincial People's Hospital. Their clinical data, histological features and immunohistochemical (IHC) results were analyzed, with review of relevant literature. Results: All 14 patients' ages ranged from 41 to 79 years (mean 55 years). There were 12 females and 2 males. All patients had non-specific symptoms, but they all had positive serum anti-parietal cell antibody and/or anti-intrinsic factor antibody. Seven patients had variable degree of anemia. Two patients had concomitant H. pylori infection. Two patients presented with multiple protruding polyps in corpus/fundus, 0.2 to 0.9 cm in diameter, or multiple large lobulated and broad based polyps (0.8 to 3.5 cm in diameters). The former cases were diagnosed as type 1 neuroendocrine tumors, the latter were multiple hyperplastic polyps. Microscopically, autoimmune gastritis showed typical morphology, characterized by diffuse corpus-restricted atrophic gastritis with variable proportions of intestinal metaplasia, or pseudopyloric metaplasia, pancreatic, acinar metaplasia, foveolar hyperplasia and hyperplasia of the endocrine-like cells (ECL cells). Hyperplasia of ECL cells often needed IHC staining to confirm. CgA/Syn IHC stain highlighted linear and micronodular ECL cell hyperplasia. In the absence of concurrent or past H. pylori infection, the antrum was usually normal. Gastrin IHC stain showed hyperplasia of gastrin-producing cells (G cells) in the antrum. Two cases were in the early phase, six were in florid phase, and six were end phase. Conclusions: Most patients of autoimmune gastritis have non-specific symptoms or are asymptomatic and show various endoscopic findings. There are three histologic phases of autoimmune gastritis. Recognition of this entity would be beneficial for pathologists to avoid misdiagnosis. Pathologists can make preferred diagnosis of autoimmune gastritis depending on the histologic clues and prompt appropriate and timely management for the patients.