GAST and gallbladder cancer: Functional tumors, due to their ability to produce hormones like serotonin, CgA, adrenocorticotropic hormone (ACTH), and gastrin, may exhibit hormone-related side effects, such as flushing, diarrhea, and coughing.[15,21,22] Most cases of gallbladder cancer do not exhibit typical clinical signs or symptoms in the early stages, and as such, they are often found at an advanced stage.