Stages of Colorectal Cancer

Staging systems categorize the progression of colorectal cancer. Cancer stage can be estimated but cannot be confirmed until after surgery, when the pathologist examines the excised polyp, tumor, or lymph nodes under a microscope. The TNM stages of colorectal cancer are numbered 0 to IV. In the TNM system, stage is based on detailed information about the tumor location and spread that includes:

• Penetration of the tumor though the colon or rectum wall, "T"

• Level of lymph node involvement, "N"

• Metastasis, or "M"

Stage 0

Stage 0 is called non-invasive or carcinoma in situ colorectal cancer. In Stage 0, cancer cells are present. However the tumor has not grown beyond the inner most layer of the colon or rectum. Cancer has not spread to any local lymph nodes and has not metastasized. There is not an equivalent stage for Stage 0 in the Modified Dukes/ Astler-Coller systems.

Stage I

In Stage I the tumor is classified as having either a T1 or a T2 level tumor:

Stage I, with a T1 tumor means that cancer has spread beyond the inner, or mucosa, layer of the colon and into a layer of supportive tissue called the submucosa. Cancer has not spread to any local lymph nodes and has not metastasized.

Stage I with a T2 tumor means that cancer has spread beyond the mucosa and the submucosa into the muscular layer of the colon, called the muscularis propria. Cancer has not spread to the lymph nodes and has not metastasized.

Stage II

There are two sub-stages in the overall Stage II category: Stage II-A and Stage II-B.

Stage II-A

In Stage II-A, the tumor is classified as a T3 tumor. This means cancer has spread beyond the mucosa, the submucosa and the muscularis propria into the outermost Serosa layers. Cancer has not spread to the lymph nodes and has not metastasized.

Stage II-B

In Stage II-B the tumor is classified a T4. This means cancer has spread beyond the outer wall of the colon or rectum and into nearby tissues or organs.

Cancer has not spread to the lymph nodes and has not metastasized.

Stage III

There are three sub-stages in the Stage III category:

Stage III-A

A Stage III-A tumor is classified as having either a T1 or a T2 level tumor.

Stage III-A with a T1 tumor means the tumor has spread beyond the mucosa and into the submucosa. Cancer has spread to one to three local lymph nodes but has not metastasized.

Stage III-A with a T2 tumor, means the tumor has spread beyond the mucosa and submucosa and penetrated the muscularis propria layer of the colon.

Cancer has spread to one to three local lymph nodes but has not metastasized.

Stage III-B

In Stage III-B, the tumor is classified as either a T3 or a T4 level tumor. Stage III-B with a T3 tumor means the tumor has spread beyond the mucosa, the submucosa, and the muscularis propria, and into the outermost serosa layer of the colon. Cancer has spread to one to three local lymph nodes, but has not metastasized.

Stage III-B with a T4 tumor means the tumor has spread beyond the outer wall of the colon or rectum and into nearby tissues or organs.

Cancer has spread to one to three or more local lymph nodes, but has not metastasized.

Stage III-C

A Stage III-C tumor can be of any T classification. This means the tumor may be restricted to the mucosa, the submucosa, the muscularis propria, into the outermost serosa layers of the colon, or it may have grown beyond the outer wall of the colon or rectum and into nearby tissues or organs. Regardless of tumor development in Stage III-C, cancer has spread to 4 or more local lymph nodes, but has not metastasized.

Stage IV

Stage IV is also known as metastatic cancer. The tumor can be any T designation. This means there may be no evidence of a tumor or it may have grown beyond the mucosa, the submucosa, the muscularis propria, into the outermost Serosa layers, or it may have grown beyond the outer wall of the colon or rectum and into nearby tissues or organs.

In Stage IV, cancer may have spread to any number of local lymph nodes. This means there may be no local nodes involved or cancer may have spread to 4 or more local lymph nodes. The distinguishing factor of Stage IV is that the cancer has metastasized to distant organs or tissues.