Determining the Extent of Colorectal Cancer
If the biopsy shows that colorectal cancer is present, your doctor needs to know the extent (stage) of the disease to recommend the best treatment plan for you. This is also referred to as staging.
One common tool used to describe the stage of cancer is the TNM system:
- Tumor (T): Has the tumor grown into the wall of the colon or rectum? How many layers?
- Node (N): Has the tumor spread to the lymph nodes? If so, where and how many?
- Metastasis (M): Has the cancer spread to other parts of the body? If so, where and how much?
The results are combined to determine the stage of cancer for each person. There are 5 stages: stage 0 (zero) and stages I through IV (1 through 4). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.
The "T" plus a letter or number (0 to 4) is used to describe how deeply the primary tumor has grown into the bowel lining.
TX: The primary tumor cannot be evaluated.
T0 (T zero): There is no evidence of cancer in the colon or rectum.
Tis: Refers to carcinoma in situ (also called cancer in situ). Cancer cells are found only in the epithelium or lamina propria, which are the top layers lining the inside of the colon or rectum.
T1: The tumor has grown into the submucosa, which is the layer of tissue underneath the mucosa or lining of the colon.
T2: The tumor has grown into the muscularis propria, a deeper, thick layer of muscle that contracts to force along the contents of the intestines.
T3: The tumor has grown through the muscularis propria and into the subserosa, which is a thin layer of connective tissue beneath the outer layer of some parts of the large intestine, or it has grown into tissues surrounding the colon or rectum.
T4a: The tumor has grown into the surface of the visceral peritoneum, which means it has grown through all layers of the colon.
T4b: The tumor has grown into or has attached to other organs or structures.
The "N" stands for lymph nodes. Lymph nodes near the colon and rectum are called regional lymph nodes. All others are distant lymph nodes that are found in other parts of the body.
NX: The regional lymph nodes cannot be evaluated.
N0 (N zero): There is no spread to regional lymph nodes.
N1a: There are tumor cells found in 1 regional lymph node.
N1b: There are tumor cells found in 2 or 3 regional lymph nodes.
N1c: There are nodules made up of tumor cells found in the structures near the colon that do not appear to be lymph nodes.
N2a: There are tumor cells found in 4 to 6 regional lymph nodes.
N2b: There are tumor cells found in 7 or more regional lymph nodes.
The "M" stands for metastasis, which describes cancer that has spread to other parts of the body, such as the liver or lungs.
M0 (M zero): The disease has not spread to a distant part of the body.
M1a: The cancer has spread to 1 other part of the body beyond the colon or rectum.
M1b: The cancer has spread to more than 1 part of the body other than the colon or rectum.
M1c: The cancer has spread to the peritoneal surface.
Stages of Colorectal Cancer