The intestines are part of the body's digestive system, which absorbs nutrients from food that is ingested. The colon and rectum comprise the latter portion of the digestive tract. They are located in the lower abdomen and are connected to the anus. Cancer in these regions is sometime called "colorectal cancer" because cancerous cells often spread quickly from one region to another. During diagnosis, the doctor will assign a stage to the cancer, which indicates the extent to which the cancer has grown and assists in determining the method and extent of treatment.
Stage 0
The Masonic Cancer Center of the University of Minnesota describes stage 0 as the earliest stage of cancer growth. In this stage of cancer of the colon and/or rectum, abnormal cells are present in the innermost lining of the colon and/or rectum. While these cells are not yet cancerous, they are different from normal cells and may transform into cancerous growth at any time. This stage of colorectal cancer is also referred to as carcinoma in situ.
Stage I
Stage I cancer of the colon and rectum involves cells that are definitely cancerous and that have grown through the inner lining of this part of the intestines into the middle muscle layer, according to the American Cancer Society. However, the cancer has not spread completely through the colon or rectum, and has not spread to lymph nodes or other distant sites in the body.
Stage II
According to the Masonic Cancer Center, stage II colon and rectal cancer is split into two sub-stages: stage IIA and stage IIB. Cancerous cells that have grown into the outermost layers of the colon and/or rectum characterize stage IIA. However, the cancer has not spread to distant sites in the body. In stage IIB cancer of the colon and rectum, the cancer has grown through the walls of these portion of the intestines, and may have attached to near by organs. The cancer may also have grown through the peritoneum, which is the layer of tissue in the abdomen that holds organs in place.
Stage III
The University of Maryland Medical center reports that stage III cancer of the colon and rectum has advanced beyond stage II by the spreading of cancerous cells to the lymph nodes.
Stage IV
The American Cancer Society states that in stage IV cancer of the colon and rectum the cancerous cells may or may not have grown through the colon and/or rectum wall. However, the distinguishing feature of stage IV colon and rectal cancer is that the cancer is detectable in one or more organs that are not located near the colon and rectum. Examples of organs to which the cancer may have spread include the lungs, bones, or liver.
