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Colorectal Cancer Staging

If the biopsy shows that cancer is present, your doctor will need to know the extent, or stage, of the disease in order to plan the best treatment. The stage is based on whether the tumor has invaded nearby tissues, whether the cancer has spread and, if so, to what parts of the body.

Staging of Colorectal Cancer

According to the American Cancer Society, the TNM system, created by the American Joint Committee on Cancer (AJCC), is the most widely used. 

TNM stands for: 

  • T: the size of the tumor and any spread of cancer into nearby tissue
  • N: the spread of cancer to nearby lymph nodes
  • M: metastasis (spread of cancer to other parts of the body)

Patients are given a T, N and M status. When combined, they determine the stage of colorectal cancer.

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.

T categories for colorectal cancer

T followed by 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: There is no evidence of cancer in the colon or rectum.
  • Tis: Refers to carcinoma in situ (also called cancer in situ). Cancer cells have not grown beyond the inner layer (mucosa) of the colon or rectum.
  • T1: The tumor has grown into the submucosa— the layer of tissue underneath the mucosa or lining of the colon or rectum.
  • T2: The tumor has grown into the muscularis propria, a deeper, thick layer of muscle that is responsible for moving food down the gut.
  • T3: The tumor has grown through the outermost layers of the colon or rectum but has not gone through them nor has it reached nearby organs..
  • T4a: The cancer has grown through all layers of the colon.
  • T4b: The cancer has grown into or has attached to other organs or structures.

N categories for colorectal cancer

N followed by a letter or number (0 to 2) indicates whether the cancer has spread to lymph nodes near the colon and rectum (called regional lymph nodes). 

  • NX: The regional lymph nodes cannot be evaluated.
  • N0: There is no spread to regional lymph nodes.
  • N1a: There are cancer cells found in 1 regional lymph node.
  • N1b: There are cancer cells found in 2 or 3 regional lymph nodes.
  • N1c: There are nodules made up of tumor cells found in areas of fat near the colon but not the nodes themselves.
  • N2a: There are cancer cells found in 4 to 6 regional lymph nodes.
  • N2b: There are cancer cells found in 7 or more regional lymph nodes.

M categories for colorectal cancer

M followed by a letter or number (0 to 1) describes cancer that has spread to other parts of the body, such as the liver or lungs. This is called distant metastasis.

  • M0: The cancer 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 distant parts of the peritoneum (the lining of the abdominal cavity). It also may or may not have spread to distant organs or lymph nodes.

The following chart from the American Cancer Society is helpful in comparing stages and the TNM status.

AJCC Stage

Stage grouping

Stage description*

0

Tis

N0

M0

The cancer is in its earliest stage. This stage is also known as carcinoma in situ or intramucosal carcinoma (Tis). It has not grown beyond the inner layer (mucosa) of the colon or rectum.

I

T1 or T2

N0

M0

The cancer has grown through the muscularis mucosa into the submucosa (T1), and it may also have grown into the muscularis propria (T2). It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

IIA

T3

N0

M0

The cancer has grown into the outermost layers of the colon or rectum but has not gone through them (T3). It has not reached nearby organs. It has not spread to nearby lymph nodes (N0) or to distant sites (M0).

IIB

T4a

N0

M0

The cancer has grown through the wall of the colon or rectum but has not grown into other nearby tissues or organs (T4a). It has not yet spread to nearby lymph nodes (N0) or to distant sites (M0).

IIC

T4b

N0

M0

The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs (T4b). It has not yet spread to nearby lymph nodes (N0) or to distant sites (M0).

 

 

 

 

IIIA

 

T1 or T2

N1/N1c

M0

The cancer has grown through the mucosa into the submucosa (T1), and it may also have grown into the muscularis propria (T2). It has spread to 1 to 3 nearby lymph nodes (N1) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites (M0).

OR

T1

N2a

M0

The cancer has grown through the mucosa into the submucosa (T1). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites (M0).

 

 

 

 

 

 

 

IIIB

 

T3 or T4a, N1/N1c

M0

The cancer has grown into the outermost layers of the colon or rectum (T3) or through the visceral peritoneum (T4a) but has not reached nearby organs. It has spread to 1 to 3 nearby lymph nodes (N1a or N1b) or into areas of fat near the lymph nodes but not the nodes themselves (N1c). It has not spread to distant sites (M0).

OR

T2 or T3

N2a

M0

The cancer has grown into the muscularis propria (T2) or into the outermost layers of the colon or rectum (T3). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites (M0).

OR

T1 or T2 N2b

M0

The cancer has grown through the mucosa into the submucosa (T1), and it may also have grown into the muscularis propria (T2). It has spread to 7 or more nearby lymph nodes (N2b). It has not spread to distant sites (M0).

 

 

 

 

 

 

IIIC

 

T4a

N2a

M0

The cancer has grown through the wall of the colon or rectum (including the visceral peritoneum) but has not reached nearby organs (T4a). It has spread to 4 to 6 nearby lymph nodes (N2a). It has not spread to distant sites (M0).

OR

T3 or T4a

N2b

M0

The cancer has grown into the outermost layers of the colon or rectum (T3) or through the visceral peritoneum (T4a) but has not reached nearby organs. It has spread to 7 or more nearby lymph nodes (N2b). It has not spread to distant sites (M0).

OR

T4b

N1 or N2

M0

The cancer has grown through the wall of the colon or rectum and is attached to or has grown into other nearby tissues or organs (T4b). It has spread to at least one nearby lymph node or into areas of fat near the lymph nodes (N1 or N2). It has not spread to distant sites (M0).

IVA

Any T

Any N

M1a

The cancer may or may not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes. (Any N). It has spread to 1 distant organ (such as the liver or lung) or distant set of lymph nodes, but not to distant parts of the peritoneum (the lining of the abdominal cavity) (M1a).

IVB

Any T

Any N

M1b

The cancer might or might not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes (Any N). It has spread to more than 1 distant organ (such as the liver or lung) or distant set of lymph nodes, but not to distant parts of the peritoneum (the lining of the abdominal cavity) (M1b).

IVC

Any T

Any N

M1c

The cancer might or might not have grown through the wall of the colon or rectum (Any T). It might or might not have spread to nearby lymph nodes (Any N). It has spread to distant parts of the peritoneum (the lining of the abdominal cavity), and may or may not have spread to distant organs or lymph nodes (M1c).

*The following additional categories are not listed in the table above:

  • TX: Main tumor cannot be assessed due to lack of information.
  • T0: No evidence of a primary tumor.
  • NX: Regional lymph nodes cannot be assessed due to lack of information.

Medical Oncologist - Colon & Rectal