The rectum serves as a reservoir, or holing area, for the stool and has remarkable sensitivity so that we are aware of when it is appropriate to move our bowels and whether the content is solid stool or intestinal gas. The wall of the hollow tube that constitutes the colorectum is made of a number of tissue types. All that the bowel can do, if irritated, is to produce in excess what it normally produces. Cancer is a disease in which abnormal cells in some organs or tissue go out of control, growing and increasing in number. Normal cells reproduce themselves throughout life, but in an orderly and controlled manner.
Normal growth occurs, worn out tissues are replaced and wounds heal.
When cells grow out of control and form a mass, the mass is called a tumor. Other tumors not only enlarge locally but also have the potential to invade and destroy the normal tissue around them and to spread to distant parts of the body. Such tumors are called malignant tumors, or cancer. Then they will have the features of tumors arising in muscular tissue, lymphoid tissue, or other tissues. The symptoms caused by cancer vary with its type and with its location along the large intestine.