Autoimmune pancreatitis misdiagnosed as a tumor of the head of the pancreas.

Autoimmune pancreatitis can mimic pancreatic cancer in its clinical presentation, imaging features and laboratory parameters. Differentiating between those two entities requires implementation of clinical judgment and experience along with objective parameters that may suggest either condition. Few strategies have been proposed for the surgeon to implement when facing borderline cases. The following case is an example of a clinical scenario compatible with an accepted algorithm for diagnosis of pancreatic cancer, which eventually proved wrong. We present a 75-year-old patient who was admitted for obstructive jaundice. Imaging features were highly suggestive for pancreatic cancer as was the carbohydrate antigen 19-9 (CA 19-9) level, leading to a decision for surgery. Pathological examination revealed autoimmune pancreatitis. Though no frank carcinoma was found, premalignant ductal changes of pancreatic intraepithelial neoplasia (PanIN) I and PanIN II were discovered throughout the pancreatic duct. Caution is advised when relying on the combination of highly suggestive radiology features and elevated levels of CA 19-9 in the diagnosis of pancreatic cancer. When the tissue diagnosis is not conclusive, obtaining IgG4 and antinuclear Ab levels is advised, to rule out the rare possibility of autoimmune pancreatitis. Patients with autoimmune pancreatitis should be followed carefully as precancerous lesions may accompany the benign disease and the correlation of these two entities has not been ruled out.