Staging In Depth

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Staging and T, N, M Categories

Three key factors are used to determine the cancer stage: T (the size of the tumor), N (if the lymph nodes are involved in the cancer) and M (if the cancer has metastasized, or spread, to other organs in the body).

T Categories

The colon and rectum walls are made up of a series of layers. The T categories describe how far through the layers the tumor may have grown. The layers are:

 Mucosa

The mucus membrane that makes up the inner lining

Muscularis mucosa

Thin layer of muscle fibers

Submucosa

Layer under the muscularis mucosa

Muscularis propria

Thick, main muscle layer

Serous membrane

Thin outermost layer that covers the colon but not the rectum

The T categories for colorectal cancer are:

Tx

The extent of the tumor cannot be determined

Tis

Cancer involves only the mucosa

T1

Tumor has grown through the muscularis mucosa and into the submucosa

T2

Tumor has grown through the submucosa and into the muscularis propria

T3

Tumor has grown through the muscularis propria and into serous membrane, but has not grown into regional (nearby) tissue or organs.

T4

Tumor has grown through the colon or rectum wall and into regional tissue or organs.

N Categories

Nx

It cannot be determined if lymph nodes are involved

N0

No cancer in the lymph nodes

N1

Cancer found in up to three regional lymph nodes

N2

Cancer found in four (or more) regional lymph nodes

M Categories

Mx

It cannot be determined if cancer has metastasized (spread)

M0

Cancer has not metastasized to any distant organs

M1

Cancer has metastasized to distant organs

Overall Staging

Once the T, N and M categories are determined, the information is combined and used to decide the overall cancer stage. Overall staging for colorectal cancer uses Stage I through Stage IV. The lower the staging number, the less advanced the cancer.

Stage

TNM category

What It Means

Stage 0

Tis, N0, M0

Earliest stage of cancer. Tumor has not grown beyond the mucosa. This stage is also known as carcinoma in situ or intramucosal carcinoma.

 Stage I

T1, N0, M0
T2, N0, M0

T1 means cancer has grown through the muscularis mucosa into the submucosa. T2 means cancer has grown through the submucosa into the muscularis propria. No lymph nodes are involved.

Stage IIA

T3, N0, M0

Cancer has grown into serous membrane but has not spread to lymph nodes or other organs.

Stage IIB

T4, N0, M0

Cancer has grown through colon or rectum wall into regional tissue or organs. Lymph nodes and distant tissue and organs are not involved.

Stage IIIA

T1, N1, M0
T2, N1, M0

T1 means cancer has grown through the mucosa into the submucosa. T2 means cancer has grown through the submucosa into the muscularis propria. Up to three lymph nodes are involved. There is no spread to distant tissue or organs.

Stage IIIB

T3, N1, M0
T4, N1, M0

T3 means cancer has grown into the serous membrane (outer most layers) but has not spread to regional organs. T4 means cancer has grown through colon or rectal wall and into regional tissue or organs. Up to three lymph nodes are involved. There is no spread to distant tissue or organs.

Stage V

Any T, Any N, M1

Cancer may or may not have grown through the colon and rectal wall. Regional lymph nodes may or may not be involved. Cancer has spread to other distant organs.


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