A Diagnostic Challenge: Pancreatic Cancer or Autoimmune Pancreatitis?

We report a rare case of seronegative autoimmune pancreatitis (AIP) that presented as a pancreatic focal lesion and was considered to be pancreatic cancer based on the clinical presentation and imaging findings. The endoscopic ultrasound-guided biopsies of the pancreatic mass revealed no malignant cells and the pancreatic swelling had become diffuse on repeat imaging. AIP was suspected and a trial of steroids was considered as a diagnostic and therapeutic method. The patient responded dramatically to corticosteroid treatment with resolution of symptoms and normal imagining and laboratory parameters. This case highlights the challenge in the diagnostic approach of a pancreatic mass.