Mass-Forming Immunoglobulin G4-Related Ampullitis Mimicking a Duodenal Subepithelial Tumor: A Case Report

Abstract

Subepithelial tumors (SETs) are often found accidentally during gastroscopy, most commonly in the stomach. If a raised lesion is observed around the major papilla, the relationship with the common bile duct or pancreas should be evaluated, and not only SET but also cancer or autoimmune disease should be considered in the differential diagnosis. Herein, we present a case of prominent major papilla mimicking a SET that was accidentally discovered during endoscopy. The patient was asymptomatic, and the physical and laboratory findings were normal. The biopsy findings were nonspecific and imaging findings suggested possible malignancy; thus, surgical ampullectomy was performed. The histopathological results confirmed IgG4-related ampullitis. This case suggests that immunoglobulin G4 (IgG4)-related disease may manifest with atypical findings, hindering its diagnosis and treatment.