An endoscopic mucosal resection (EMR) is a procedure to remove precancerous, early-stage cancerous tissues (lesions) from the digestive tract. Mucosal resection is performed using an endoscopic device that consists of a long, narrow tube that has a light, a video camera, and other instruments. The endoscope is passed down the throat to find abnormalities in the esophagus, stomach, or upper portion of the small intestine (duodenum) during EMR of the upper digestive tract. Through the anus, the tube is guided up to remove lesions from the colon. EMR is primarily used for treating patients, but it can also be used to collect tissues for diagnosis. EMR can determine whether cancer has invaded tissues beneath the digestive tract lining if cancer is present.