Reconsidering pancreatic masses: A case of IgG4-related autoimmune pancreatitis mimicking malignancy.

Autoimmune pancreatitis (AIP) is an uncommon, immune-mediated form of chronic pancreatitis characterized by lymphoplasmacytic infiltration, fibrosis, and frequently elevated serum IgG4 levels. Clinically and radiologically, AIP often mimics pancreatic ductal adenocarcinoma, posing a substantial diagnostic challenge that risks unnecessary surgical interventions. This article presents the case of a 53-year-old female patient with epigastric pain, obstructive jaundice, and a pancreatic head mass initially suggestive of malignancy. Detailed imaging (CT, MRI, MRCP), serological evaluation showing elevated IgG4, and a favorable response to corticosteroid therapy confirmed the diagnosis of type 1 AIP. The case underscores the importance of accurately differentiating AIP from pancreatic malignancies by integrating clinical data, imaging features-particularly the absence of significant double-duct dilatation characteristic of pancreatic cancer-the presence of renal lesions, which represent an unusual metastatic site in pancreatic malignancies, serological markers, histopathological findings, and steroid responsiveness. Early diagnosis is crucial to avoid unwarranted surgery, initiate appropriate immunosuppressive treatment, and ensure favorable long-term outcomes. This report contributes to the growing body of evidence highlighting AIP's diagnostic complexity and underscores the necessity for a multidisciplinary approach in its management.