BACKGROUND: The choice between 22-gauge endoscopic ultrasound-guided fine-needle biopsy (EUS-FNB) and EUS-guided fine-needle aspiration (EUS-FNA) for histological diagnosis of type 1 autoimmune pancreatitis (AIP) is unclear. We retrospectively examined the detection rate of histological findings for AIP using EUS-FNA/FNB. METHODS: Patients diagnosed with type 1 AIP using EUS-FNB (Franseen needle) or EUS-FNA (conventional needle) with 22-gauge needles at our hospital between 2012 and 2023 were included in this study. AIP was diagnosed according to International Consensus Diagnostic Criteria (ICDC). The detection rates of level 1 findings, which included storiform fibrosis and/or obliterative phlebitis, and level 2 histological findings were evaluated according to the ICDC. RESULTS: The EUS-FNB and EUS-FNA groups included 25 and 24 patients, respectively. No significant differences in patient background were noted between the two groups. The detection rates of prominent filtration of lymphocytes and plasma cells along with fibrosis were 56.0% in the EUS-FNB group and 12.5% in the EUS-FNA group (p = .001). The detection rates of more than 10 IgG4-positive plasma cells per high-power microscopic field were 68.0% and 29.2% in the EUS-FNB and EUS-FNA groups, respectively (p = .007). The histological findings for levels 1 and 2 were significantly higher in the EUS-FNB group (56.0% vs. 12.5%
p = .001). Mild pancreatitis was observed in the EUS-FNB group
however, no other serious adverse events occurred. CONCLUSION: The 22-gauge EUS-FNB yielded a higher rate of histological findings than 22-gauge EUS-FNA, suggesting that 22-gauge EUS-FNB is suitable and safe for the histological diagnosis of type 1 AIP.