EUS guided FNA for diagnosing autoimmune pancreatitis: Does it enhance existing consensus criteria?
Histopathology has long been considered a diagnostic reference standard for most chronic inflammatory and neoplastic diseases. The challenges associated with pancreatic tissue acquisition have resulted in a debate regarding the need and the best approach for pretreatment histologic confirmation in patients with AIP. Autoimmune pancreatitis (AIP) in many cases, remains a diagnostic challenge. Even in cases in which there is a strong clinical suspicion, the diagnosis can be difficult to confirm. In an attempt to standardize diagnostic criteria, the International Consensus Diagnostic Criteria (ICDC) were published in 2011 based on a combination of imaging, serology, organ involvement, core biopsy findings, and response to corticosteroids. In the absence of a standalone pathognomonic blood biomarker or radiologic or endosonographic feature, the concomitant presence of any 3 of the following 4 key histopathologic findings was considered to provide the highest level of diagnostic reliability: lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis, and >10 IgG4positive cells per high power field (HPF) Most studies in recent times have used that as a reference standard for comparing other diagnostic approaches. EUS provides the ability to acquire pancreatic tissue either by FNA or core biopsy and has potential utility not only in establishing the diagnosis of AIP but also in excluding other pancreatic diseases that can mimic AIP, such as pancreatic cancer. However, although core biopsy findings are accepted diagnostic criteria, cytology does not feature in the ICDC. Until recently, the role of EUS guided FNA (EUS FNA) in the diagnosis of AIP had not been studied extensively. This study, along with a few others in the recent past, has provided valuable insight into the diagnostic utility of EUS FNA in AIP. A consensus panel of pancreas pathologists ruled that pancreatic EUS FNA is insufficient to make a firm diagnosis of AIP (Hawaii Consensus) The main limitation of FNA cytology is that it does not provide tissue architecture to allow histopathologic diagnosis. Only 1 of 4 diagnostic criteria can be assessed by FNA cytology (namely, Ig4th cells) and that alone is insufficient to suspect or confirm a diagnosis of AIP. FNA biopsy infrequently and variably yields bits of pancreatic tissue allowing for study of tissue architecture. Therefore, previous studies have reported variable diagnostic yield with the use of 22 gauge EUSFNA needles in patients with AIP. There is a lack of consensus on what constitutes an adequate FNA sample for the purpose of diagnosis and the acceptable range
Gastrointestinal endoscopy