INTRODUCTIONWith endoscopic ultrasound (EUS) guidance, it is possible to obtain tissue or fluid samples from all lesions at a distance of not more than 5-6 cm, which is the distance the echoendoscope can reach. EUS enables a gastroenterologist to sample the masses of the middle and inferior mediastinum, which are adjacent to the esophagus; cystic or solid lesions of the pancreas, which are adjacent to the stomach and duodenum; perirectal lesions; subepithelial lesions of the upper gastrointestinal tract; upper abdominal masses; and lesions located in the left kidney, left adrenal gland, and left lobe of the liver by fine-needle aspiration (FNA) or core biopsy.