Abstract
Autoimmune pancreatitis (AIP) is a unique form of pancreatitis in which autoimmune mechanisms are suspected to be involved in its pathogenesis. AIP is currently diagnosed based on the International Consensus Diagnostic Criteria (ICDC). Although the use of resected or core biopsy specimens are recommended for the histological classification according to the ICDC, it is difficult to collect adequate pancreatic biopsy specimens for detailed examination. With the widespread use of EUS-guided FNA (EUS-FNA) cytology and histology, these have become essential modalities for the diagnosis of pancreatic diseases. We here present tips for the diagnosis of AIP by EUS-FNA. Because adequate collection of pancreatic tissue depends on how fast the needle is moved within the pancreas, it is crucial to insert the aspiration needle as quickly as possible. For this purpose, a spring-loaded biopsy needle or a manual aspiration needle such as the Boston Expect, which has a strong needle stopper and a stiff needle, is useful. Adequate processing of histological specimens is another important point. The aspirated tissues are pushed out on a glass slide using a syringe. Tubifex-like pieces of tissue in the blood are picked up and transferred to another formalin-filled dish. The pancreatic tissue is trimmed with disposable 18-G needles and transferred to another formalin-filled container for pathological examination. We usually can obtain histological samples adequate for the assessment of IgG4-positive plasma cells and obliterative phlebitis. EUS-FNA provides adequate histological samples for the diagnosis of AIP and therefore may help to increase the value of ICDC in diagnosing AIP as well as determining the type of AIP.
