Understanding a diagnosis by stage

Stage 0: This is the earliest stage. Cancer has not moved from where it started; it's still restricted to the innermost lining of the colon. Known as ‘cancer in situ’, meaning the cancer is in the mucosa (moist tissue lining the colon).

Stage I: Cancer is still in the inner lining, but has grown through the mucosa of the colon and invaded the muscle layer.

Stage II: Colon cancer is divided into stage IIA, stage IIB and stage IIC. The cancer has grown beyond the mucosa of the colon but has not spread to the lymph nodes:

• Stage IIA: Cancer has spread through the muscle layer of the colon wall to the serosa (outermost layer) of the colon wall.
• Stage IIB: Cancer has spread through the serosa (outermost layer) of the colon wall but has not spread to nearby organs.
• Stage IIC: Cancer has spread through the serosa (outermost layer) of the colon wall to nearby tissue.

Stage III: Colon cancer is divided into stage IIIA, stage IIIB, and stage IIIC. The cancer has spread to the lymph nodes near the colon, it has not spread further:  

• Stage IIIA: Cancer has spread from the innermost tissue layer of the colon wall to the middle layers and has spread to as many as three lymph nodes.
• Stage IIIB: Cancer has spread to as many as three nearby lymph nodes and has spread:
  • beyond the middle tissue layers of the colon wall; or
  • to nearby tissues around the colon or rectum; or
  • beyond the colon wall into nearby organs and/or through the peritoneum.
• Stage IIIC: Cancer has spread to four or more nearby lymph nodes and has spread:
  • to or beyond the middle tissue layers of the colon wall; or
  • to nearby tissues around the colon or rectum; or
  • to nearby organs and/or through the peritoneum.

Stage IV: In Stage IV, colon cancer is divided into stages IVA, IVB, and IVC. The cancer has spread outside of the colon and has been carried through the lymph and blood systems to distant parts of the body, this is known as metastasis. The most likely organs to develop metastasis from colorectal cancer are the lungs and liver. 

• Stage IVA: Cancer has spread to one area or organ that is not near the colon, such as the liver, lung, ovary, or a distant lymph node.
• Stage IVB: Cancer has spread to more than one area or organ that is not near the colon, such as the liver, lung, ovary, or a distant lymph node.
• Stage IVC: Cancer has spread to the tissue that lines the wall of the abdomen and may have spread to other areas or organs.

Stage 0: In stage 0, abnormal cells are found in the innermost lining of the rectum. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I: In stage I, cancer has formed and spread beyond the innermost lining of the rectum to the second and third layers and involves the inside wall of the rectum, but it has not spread to the outer wall of the rectum or outside the rectum.

Stage II: In stage II, cancer has spread outside the rectum to nearby tissue, but it has not gone into the lymph nodes (small, bean-shaped structures found throughout the body that filter substances in a fluid called lymph and help fight infection and disease).

Stage III: In stage III, cancer has spread to nearby lymph nodes, but it has not spread to other parts of the body.

Stage IV: In stage IV, cancer has spread to other parts of the body, such as the liver, lungs, or ovaries.