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.