Staging

Staging is a way of describing a cancer, such as where it is located, if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient’s prognosis (chance of recovery). There are different stage descriptions for different types of cancers.

One tool that doctors use to describe the stage is the TNM system. This system uses three criteria to judge the stage of the cancer: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:

• How large is the primary tumor and where is it located? (Tumor, T)
  
  
• Has the tumor spread to the lymph nodes? (Node, N)
  
  
• Has the cancer metastasized (spread) to other parts of the body? (Metastasis, M)

Tumor. Using the TNM system, the "T" plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are also divided into smaller groups that help describe the tumor in even more detail. Specific tumor stage information is listed below:

TX: The primary tumor cannot be evaluated.

T0: There is no tumor.

Tis: Refers to carcinoma in situ (which is very early cancer that has not spread.)

T1: The tumor is no larger than 2 centimeters (cm).

T2: The tumor is larger than 2 cm, but not larger than 5 cm.

T3: The tumor is larger than 5 cm.

T4: The tumor has invaded other organs, such as the vagina, urethra, or bladder.

Node. The “N” in the TNM staging system stands for lymph nodes, the tiny, bean-shaped organs that help fight infection. Lymph nodes near the anus are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.

NX: Regional lymph nodes cannot be evaluated.

N0 (N plus zero): There is no regional lymph node metastasis.

N1: Cancer had spread to the perirectal (around the rectum) lymph nodes.

N2: Cancer has spread to the internal iliac (pelvic) and/or the inguinal lymph nodes (lymph nodes in the groin just under the skin surface) on the same side of the body.

N3: Cancer had spread to the perirectal and inguinal lymph nodes and/or the internal iliac and/or inguinal lymph nodes on both sides of the body.

Distant metastasis. The “M” in the TNM system indicates whether the cancer has spread to other parts of the body.

MX: Distant metastasis cannot be evaluated.

M0 (M plus zero): There is no distant metastasis.

M1: There is metastasis to other parts of the body.

Cancer stage grouping

Doctors assign the stage of the cancer by combining the T, N, and M classifications.

Stage 0: Abnormal cells are in the first layer of the lining of the anus only. The abnormal cells may become cancer. This stage is also called carcinoma in situ (Tis, N0, M0).

Stage I: The tumor is no larger than 2 cm with no spread to lymph nodes or other parts of the body (T1, N0, M0).

Stage II: The tumor is larger than 2 cm with no spread to lymph nodes or other parts of the body (T2 or T3, N0, M0).

Stage IIIA: The tumor may be any size and has spread to either nearby lymph nodes or to organs, such as the vagina, urethra, and bladder (T1, T2, T3; N1, M0; or T4, N0, M0).

Stage IIIB: The tumor may be any size and has spread to nearby lymph nodes or organs; lymph nodes in the pelvis and/or groin; or to lymph nodes near the rectum, in the groin and/or on both sides of the pelvis or groin (T4, N1, M0; or Any T, N2 or N3, M0).

Stage IV: The tumor may be any size and has spread to lymph nodes and to distant parts of the body (Any T, Any N, M1).

Recurrent: Recurrent cancer is cancer that comes back after treatment.

Grading

Histologic grade (G). In addition to the TNM system, doctors may also assign a histologic grade to the cancer. Histologic grade indicates how closely the cancer cells resemble normal tissue under a microscope. A tumor's grade is described using the letter “G” and a number.

GX: The tumor grade cannot be identified.

G1: Describes cells that look more like normal tissue cells (well differentiated).

G2: The cells are somewhat different from normal cells (moderately differentiated).

G3: The cells do not look like normal cells (poorly differentiated).

G4: Describes tumor cells that barely resemble normal cells (undifferentiated).

Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.cancerstaging.net.