This is a descriptive analytical study to investigate the prevalence and risk factors for pancreatitis after Endoscopic Ultrasonography-guided Fine Needle Biopsy (EUS-FNB) in patients at Shariati Hospital in Tehran. The study aims to identify risk factors for post-FNB pancreatitis to improve clinical protocols, reduce complications and treatment costs, and increase diagnostic accuracy for pancreatic and biliary tract diseases. The study will collect demographic and clinical data from all eligible patients undergoing EUS-guided FNB during the study period. Amylase and lipase levels will be measured in all enrolled patients 24 hours post-procedure. Pancreatitis will be diagnosed based on abdominal pain and amylase or lipase levels exceeding three times the normal range 24 hours after the procedure. The outcomes will be independently adjudicated by an expert gastroenterologist not involved in the EUS procedures by reviewing participants' medical records. The consensus definition will be applied as a diagnostic framework (rather than a strict definition) so that the adjudicator can use their best judgment in cases that does not strictly satisfy the criteria. The patients will be contacted 24-72 h after the procedure to follow-up on any potential complications. The study plans to enroll at least 300 patients.