After we confirm you have anal cancer, the next step is to find out the cancer stage. Staging is a way of saying how far along the cancer is. We may suggest tests, such as CT and MRI scans, to see if the cancer has spread. Staging helps your care team understand your anal cancer so they can offer the best treatment.

Our doctors use a staging method from the American Joint Committee on Cancer. It’s called the TNM system. We will tell you the stage of the tumor using the numbers and letters below. We will explain what they mean when we talk with you about the stage.

TNM System

Your doctor will use letters and numbers to help describe the stage of the cancer:

• T is the size of the tumor.
• N is whether the cancer has spread to the lymph nodes (small structures that are part of the immune system).
• M is whether the cancer has metastasized (spread) to other parts of the body.

Anal cancer is sorted into 5 stages:

• Stage 0 is very early anal cancer that is found only in the top layer of the lining of the anus.
• Stage 1 tumors are small (less than 2 centimeters, or smaller than the size of a peanut). The cancer has not spread outside the anus.
• Stage 2 anal cancer tumors are larger than 2 centimeters but have not spread.
• Stage 3 anal cancer has spread to nearby lymph nodes.
• Stage 4 anal cancer has spread to nearby lymph nodes and other parts of the body.

Your MSK doctor may talk with you about having the tumor analyzed by MSK-IMPACT™. MSK developed this genetic-sequencing test. It can help people with advanced anal cancer that has not responded to treatment. MSK-IMPACT is approved by the U.S. Food and Drug Administration. This test looks for certain genetic mutations (changes) in the tumor. We use this information to find a clinical trial that’s right for you.