Digestive System Neoplasms are abnormal growths that occur in the digestive system. They can occur in any part of the digestive tract, including the esophagus, stomach, small intestine, large intestine, rectum, and anus. These neoplasms can be benign or malignant and can cause a variety of symptoms, such as abdominal pain, bloating, weight loss, and changes in bowel habits.