Endoscopic ultrasound-guided fine needle aspiration in the differentiation of type 1 and type 2 autoimmune pancreatitis

AIM: To investigate the usefulness of endoscopic ultrasound- guided fine needle aspiration (EUS-FNA) in the differentiation of autoimmune pancreatitis (AIP). METHODS: We retrospectively reviewed 47 of 56 AIP patients who underwent EUS-FNA and met the Asian diagnostic criteria. On 47 EUS-FNA specimens, we evaluated the presence of adequate material and characteristic features of lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric pancreatitis (IDCP) mentioned in the International Consensus Diagnostic Criteria and examined if these findings make a contribution to the differential diagnosis of type 1 and type 2 AIP. A disposable 22-gauge needle was used for EUS-FNA. RESULTS: Adequate specimens including pancreatic tissue for differentiating AIP from cancer were obtained from 43 of 47 patients who underwent EUSFNA. EUS-FNA was performed from the pancreatic head in 21 cases, which is known to be technically difficult when performed by core biopsy; there was no significant difference in the results compared with pancreatic body-tail. Nine of 47 patients met level 1 findings of LPSP and 5 patients met level 2 findings of LPSP. No one met level 1 findings of IDCP, but 3 patients met level 2 findings of IDCP. Of 10 seronegative cases, 2 cases were diagnosed with "definitive type 1 AIP", and 3 cases were diagnosed with "probable type 2 AIP" when considering both the level 2 histological findings and response to steroids. CONCLUSION: EUS-FNA is useful in the differentiation of type 1 and type 2 AIP, particularly in seronegative cases.