For example, tumors from enterochromaffin cells of the gastrointestinal tract cause the formation of stones in the gallbladder, lead to hypersecretion of gastric and pancreatic juice, hyperplasia of the mucous membrane, increase peristalsis, fibrosis of the myocardium and peritoneum, as well as necrotic changes in the skincurrent is often manifested by disorders of hormone processing. Therefore, tumor cells can secrete prohormones (for example, some insulinomas secrete significant concentrations of proinsulin)