A case of pancreatic ductal adenocarcinoma concomitant with IgG4-related disease in the pancreas and the stomach.

A 75-year-old Japanese woman visited a hospital with a stomachache. The patient was diagnosed with localized mild acute pancreatitis. Blood tests revealed elevated serum IgG4 levels. Contrast-enhanced computed tomography showed a hypovascular mass, 3 cm in size, in the pancreatic body with dilation of the upstream duct. Additionally, it showed another tumorous lesion of 10 mm in size in the anterior wall of the stomach, and endoscopic examination confirmed a submucosal tumor (SMT) sized 10 mm in the anterior wall of the stomach. Endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNAB) of the pancreas revealed an adenocarcinoma concomitant with marked IgG4-positive cell infiltration. Hence, distal pancreatectomy with local gastrectomy was performed, and the final diagnosis was concluded as pancreatic ductal adenocarcinoma (PDAC) complicated by IgG4-related diseases (IgG4-RD) in the pancreas and stomach. IgG4-RD of the digestive tract is exceedingly rare. The correlation between PDAC and autoimmune pancreatitis or malignancy and IgG4-RD is controversial. However, the clinical course and histopathological examination, in this case, provide valuable suggestive findings for further discussion.