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Stages of Colon Cancer

After colon cancer has been diagnosed, tests are done to find out if cancer cells have spread within the colon or to other parts of the body.

The process used to find out if cancer has spread within the colon or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment.

The following tests and procedures may be used in the staging process:

  • CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, such as the abdomen, pelvis, or chest, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.
  • MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the colon. A substance called gadolinium is injected into the patient through a vein. The gadolinium collects around the cancer cells so they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).
  • PET scan (positron emission tomography scan): A procedure to find malignant tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Malignant tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.
  • Chest x-ray: An x-ray of the organs and bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
  • Surgery: A procedure to remove the tumor and see how far it has spread through the colon.
  • Lymph node biopsy: The removal of all or part of a lymph node. A pathologist views the tissue under a microscope to look for cancer cells. This may be done during surgery or by endoscopic ultrasound-guided fine needle aspiration biopsy.
  • Complete blood count (CBC): A procedure in which a sample of blood is drawn and checked for the following:
    • The number of red blood cells, white blood cells, and platelets.
    • The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.
    • The portion of the blood sample made up of red blood cells.
  • Carcinoembryonic antigen (CEA) assay: A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of colon cancer or other conditions.

There are three ways that cancer spreads in the body.

Cancer can spread through tissue, the lymph system, and the blood:

  • Tissue. The cancer spreads from where it began by growing into nearby areas.
  • Lymph system. The cancer spreads from where it began by getting into the lymph system. The cancer travels through the lymph vessels to other parts of the body.
  • Blood. The cancer spreads from where it began by getting into the blood. The cancer travels through the blood vessels to other parts of the body.

Cancer may spread from where it began to other parts of the body.

When cancer spreads to another part of the body, it is called metastasis. Cancer cells break away from where they began (the primary tumor) and travel through the lymph system or blood.

  • Lymph system. The cancer gets into the lymph system, travels through the lymph vessels, and forms a tumor (metastatic tumor) in another part of the body.
  • Blood. The cancer gets into the blood, travels through the blood vessels, and forms a tumor (metastatic tumor) in another part of the body.

The metastatic tumor is the same type of cancer as the primary tumor. For example, if colon cancer spreads to the lung, the cancer cells in the lung are actually colon cancer cells. The disease is metastatic colon cancer, not lung cancer.

The following stages are used for colon cancer:

Stage 0 (Carcinoma in Situ)

In stage 0, abnormal cells are found in the mucosa (innermost layer) of the colon wall. 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 colon cancer, cancer has formed in the mucosa (innermost layer) of the colon wall and has spread to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the colon wall.

Stage II

Stage II colon cancer is divided into stages IIA, IIB, and IIC.

  • 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 to the tissue that lines the organs in the abdomen (visceral peritoneum).
  • Stage IIC: Cancer has spread through the serosa (outermost layer) of the colon wall to nearby organs.

Stage III

Stage III colon cancer is divided into stages IIIA, IIIB, and IIIC.

In stage IIIA, cancer has spread:

  • through the mucosa (innermost layer) of the colon wall to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the colon wall. Cancer has spread to one to three nearby lymph nodes or cancer cells have formed in tissue near the lymph nodes; or
  • through the mucosa (innermost layer) of the colon wall to the submucosa (layer of tissue next to the mucosa). Cancer has spread to four to six nearby lymph nodes.

In stage IIIB, cancer has spread:

  • through the muscle layer of the colon wall to the serosa (outermost layer) of the colon wall or has spread through the serosa to the tissue that lines the organs in the abdomen (visceral peritoneum). Cancer has spread to one to three nearby lymph nodes or cancer cells have formed in tissue near the lymph nodes; or
  • to the muscle layer or to the serosa (outermost layer) of the colon wall. Cancer has spread to four to six nearby lymph nodes; or
  • through the mucosa (innermost layer) of the colon wall to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the colon wall. Cancer has spread to seven or more nearby lymph nodes.

In stage IIIC, cancer has spread:

  • through the serosa (outermost layer) of the colon wall to the tissue that lines the organs in the abdomen (visceral peritoneum). Cancer has spread to four to six nearby lymph nodes; or
  • through the muscle layer of the colon wall to the serosa (outermost layer) of the colon wall or has spread through the serosa to the tissue that lines the organs in the abdomen (visceral peritoneum). Cancer has spread to seven or more nearby lymph nodes; or
  • through the serosa (outermost layer) of the colon wall to nearby organs. Cancer has spread to one or more nearby lymph nodes or cancer cells have formed in tissue near the lymph nodes.

Stage IV

Stage IV colon cancer is divided into stages IVA, IVB, and IVC.

  • 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.
This information is not intended to replace the advice of a doctor. Navigating Care disclaims any liability for the decisions you make based on this information. This information was sourced and adapted from Adapted from the National Cancer Institute's Physician Data Query (PDQ®) Cancer Information Summaries on www.cancer.gov.

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