Focal Autoimmune Pancreatitis: A Simple Flow Chart for a Challenging Diagnosis

Autoimmune pancreatitis is a chronic fibroinflammatory autoimmune mediated disease of the pancreas. Clinically, the obstructive painless jaundice and the upper abdominal pain are the main presentations. Focal AIP is characterized by a segmental involvement of the pancreatic parenchyma and it is often radiologically represented by a pancreatic mass. In these cases, the diagnosis can be very challenging, as the main diagnostic problem is that it may be easily confused with pancreatic cancer. Therefore, as diagnostic workup, we suggest a combined approach of imaging tests. EUS study combined with CEUS and elastography, if available, increases the accuracy of the method to rule out cancer. Moreover, the lesion should always be EUS-guided sampled, obtaining a cyto/histological diagnosis. The diagnostic work up should also include the use of diagnostic clinical criteria (extrapancreatic lesions, steroid response) and laboratory findings (CA 19.9 and IgG4 evaluations).