[A Rare Case of Gastric Cancer Associated with IgG4-Related Disease].

We report a rare case of gastric cancer associated with immunoglobulin G4-related disease(IgG4-RD). A 79-year-old male was admitted to our hospital for evaluation of hepatic dysfunction. Laboratory investigations revealed elevated serum levels of AST, ALT, ALP, γ-GTP, and IgG4. Contrast-enhanced abdominal computed tomography(CT)showed diffuse wall thickening of the common bile duct(CBD), pancreatic enlargement with a capsule-like rim, and no dilatation of the main pancreatic duct. Additionally, a gastric tumor was identified. Upper gastrointestinal endoscopy revealed a type 2 tumor in the gastric antrum. The patient subsequently underwent laparoscopic distal gastrectomy with D1 lymphadenectomy and Billroth Ⅱ reconstruction. Histopathological examination confirmed the coexistence of gastric cancer and IgG4-RD. At 1-year postoperative follow-up, no evidence of tumor recurrence or progression of IgG4-RD was observed. This case underscores the importance of considering IgG4-RD in the differential diagnosis of patients presenting with both pancreaticobiliary abnormalities and gastric lesions.