The thought of potentially having cancer is stressful enough without undergoing an invasive biopsy to diagnose it and finding out that the procedure needs to be repeated due to inadequate sample collection. This project aims to optimize strategies for acquiring tissue samples to assist gastroenterologists (and pathologists) in diagnosing many diseases, including cancers. Relying on endoscopic ultrasound guidance, the two methods currently utilized are fine needle aspiration, which is the gold standard, and a new method called fine needle biopsy. Drs. Komanduri and Schenck are conducting the largest study to date to compare these different strategies. After collecting data from patients who have undergone one of these procedures over a five-year period, the investigator will perform advanced statistical modeling to determine the strategy that best optimizes patient outcomes (including obtaining accurate diagnoses and minimizing repeat invasive procedures) and costs. Once identified, this strategy will ultimately be implemented throughout the Northwestern Digestive Health Center to enhance patient care