Use of Samples From Endoscopic Ultrasound–Guided 19-Gauge Fine-Needle Aspiration in Diagnosis of Autoimmune Pancreatitis

Background & Aims Histologic techniques are used to distinguish autoimmune pancreatitis (AIP) from pancreatic malignancies and to confirm the etiology of pancreatitis. Endoscopic ultrasound–guided fine-needle aspiration (EUS-FNA) is a well-established technique used in the diagnosis of pancreatic cancer. However, it is unclear whether specimens obtained from pancreatic lesions by EUS-FNA are adequate for the histologic diagnosis of AIP, because the evaluation of tissue architecture and immunostaining assays usually require larger samples. Methods We evaluated samples collected by EUS-FNA with a conventional 19-gauge needle by histologic analysis, looking for features of AIP. We analyzed data from 44 patients who were diagnosed with AIP and underwent EUS-FNA with a 19-gauge needle from January 2004 to September 2010. The FNA specimens were reviewed by histologic analysis; AIP was diagnosed based on the presence of lymphoplasmacytic sclerosing pancreatitis or immunoglobulin (Ig)G4-positive plasma cells in the infiltrate. Results The specimen amount was inadequate from 3 patients. Among the remaining 41 patients, histopathologic analysis revealed lymphoplasmacytic sclerosing pancreatitis in 17 samples and IgG4-positive plasma cells in 5 (3 samples were positive for both); no samples had granulocytic epithelial lesions. Therefore, 19 patients (43%) were diagnosed with AIP based on histologic analysis. One patient had temporary abdominal pain. Conclusions EUS-FNA, with a 19-gauge needle, is a safe and reliable procedure for obtaining pancreatic samples for the histologic analysis of AIP. Although it does not have a high diagnostic yield, it might be useful in patients without typical features of AIP because it would allow patients to avoid surgery.