Association between autoimmune pancreatitis and pancreatic cancer: a case after long-term steroid therapy.

Autoimmune pancreatitis is a rare immunoglobulin G4-related disease characterized by a favorable response to steroids. However, its association with pancreatic cancer remains unclear. We report the case of a 71-year-old male who developed pancreatic cancer 1 month after completing a 7-year course of steroid therapy for autoimmune pancreatitis. Initially diagnosed based on elevated serum immunoglobulin G4 levels and characteristic imaging findings, the patient's autoimmune pancreatitis remained in remission during steroid therapy. Post-treatment imaging, positron emission tomography revealed a pancreatic tail mass leading to the differential diagnosis of autoimmune pancreatitis relapse versus pancreatic cancer. Histopathological examination confirmed adenocarcinoma, and the patient underwent successful neoadjuvant chemoradiotherapy and surgical resection. This case highlights the diagnostic challenges in distinguishing autoimmune pancreatitis from pancreatic cancer and emphasizes the importance of vigilant and long-term surveillance of patients with autoimmune pancreatitis, even in those with prolonged remission. Advanced imaging modalities and histopathological confirmation are essential for timely and accurate diagnosis.