ON THIS PAGE: You will learn about how doctors describe a cancer’s growth or spread. This is called the stage. In addition, you can read about how doctors evaluate and compare cancer cells to healthy cells, called grading. Use the menu to see other pages.
What is cancer staging?
Staging is a way of describing where the cancer is located, if or where it has spread, and whether it is affecting other parts of the body.
Doctors use diagnostic tests to find out the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor recommend the best kind of treatment and can help predict a patient’s prognosis, which is the chance of recovery. There are different stage descriptions for different types of cancer.
This page provides detailed information about the system used to find the stage of anal cancer and the stage groups for anal cancer, such as stage II or stage IV.
TNM staging system
One tool that doctors use to describe the stage is the TNM system. Doctors use the results from diagnostic tests and scans to answer these questions:
Tumor (T): How large is the primary tumor? Where is it located?
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 of anal cancer: 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.
Here are more details on each part of the TNM system for anal cancer:
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. Tumor size is measured in centimeters (cm). A centimeter is roughly equal to the width of a standard pen or pencil.
Stage may also be 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 (T zero): There is no tumor.
Tis: Carcinoma in situ (early cancer that has not spread to other tissue) is present.
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 urethra, bladder, or vagina.
The “N” in the TNM staging system stands for lymph nodes, the small, 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 zero): There is no regional lymph node metastasis.
N1: Cancer had spread to the inguinal (groin), perirectal (around the rectum), internal iliac (pelvic) or external iliac nodes.
N1a: Cancer has spread to the inguinal (groin), perirectal (around the rectum), or internal iliac (pelvic) lymph nodes on the same side of the body.
N1b: Cancer has spread to external iliac (pelvic) lymph nodes
N1c: Cancer has spread to the inguinal (groin), perirectal (around the rectum), or internal iliac (pelvic) lymph nodes, and to the external iliac nodes
The “M” in the TNM system describes whether the cancer has spread to other parts of the body, called metastasis.
MX: Distant metastasis cannot be evaluated.
M0 (M zero): There is no distant metastasis.
M1: There is metastasis to other parts of the body.
Doctors also describe anal cancer by its grade (G). The grade describes how much cancer cells look like healthy cells when viewed under a microscope.
The doctor compares the cancerous tissue with healthy tissue. Healthy tissue usually contains many different types of cells grouped together. If the cancer looks similar to healthy tissue and has different cell groupings, it is called “differentiated” or a “low-grade tumor.” If the cancerous tissue looks very different from healthy tissue, it is called “poorly differentiated” or a “high-grade tumor.” The cancer’s grade may help the doctor predict how quickly the cancer will spread. In general, the lower the tumor’s grade, the better the prognosis.
GX: The tumor grade cannot be identified.
G1: The cells 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: The cells barely resemble normal cells (undifferentiated).
Stage groups for anal cancer
Doctors assign the stage of the cancer by combining the T, N, M. The doctor will also include G as well.
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 and has not spread to the lymph nodes or other parts of the body (T1, N0, M0).
Stage II: The tumor is larger than 2 cm in size, but does not invade nearby organs, has not spread to the lymph nodes, and has not spread to other parts of the body (T2 or T3, N0, M0).
Stage IIIA: The tumor is 5 cm or less in size and has not invaded nearby organs, but there is spread to nearby lymph nodes without spread to other organs (T1 or T2, N1, M0).
Stage IIIB: The tumor has invaded other nearby organs, but without lymph node spread, and without disease spread to distant organs (T4, N0, M0).
Stage IIIC: The tumor is 5 cm or more in size and/or has invaded nearby organs, with spread to nearby lymph nodes but without spread to other, distant organs (T3 or T4, N1, M0).
Stage IV: The tumor may be any size and has spread to the lymph nodes and to distant parts of the body (any T, any N, M1).
Recurrent: Recurrent cancer is cancer that has come back after treatment. If the cancer does return, there will be another round of tests to learn about the extent of the recurrence. These tests and scans are often similar to those done at the time of the original diagnosis.
Used with permission of the American College of Surgeons, Chicago, Illinois. The original and primary source for this information is the AJCC Cancer Staging Manual, Eighth Edition (2017) published by Springer International Publishing.
Information about the cancer’s stage will help the doctor recommend a specific treatment plan. The next section in this guide is Types of Treatment. Use the menu to choose a different section to read in this guide.