Cancer Staging

Posted September 14, 2022 by Anusha ‐ 4 min read

Staging is a way to describe a cancer. The cancer's stage tells you where a cancer is located and its size, how far it has grown into nearby tissues, and if it has spread to nearby lymph nodes or other parts of the body. Before starting any cancer treatment, doctors may use physical exams, imaging scans, and other tests to determine a cancer's stage. Staging may not be completed until all the tests are finished.

Why does cancer staging matter?

Staging helps your doctor plan the best treatment. This may include choosing a type of surgery and whether or not to use chemotherapy or radiation therapy.

Knowing the cancer stage lets your entire health care team talk about your diagnosis in the same way.

Doctors can also use staging to:

  • Understand the chance that the cancer will come back or spread after the original treatment.

  • Help forecast the prognosis, which is the chance of recovery

  • Help determine which cancer clinical trials may be open to you.

  • See how well a treatment worked

  • Compare how well new treatments work among large groups of people with the same diagnosis

What is the TNM staging system?

  • Doctors use the TNM staging system for most types of cancer.

  • The TNM system uses letters and numbers to describe the tumor (T), lymph nodes (N), whether or not the cancer has spread or metastases (M).

  • Each letter and number tell you something about the cancer.

  • The specific definitions for each category are different for each type of cancer that is staged using this system.

Tumor (T)

The letter T and the number after it describe the tumor by answering these questions:

  • How large is the primary tumor?

  • Does it go into other tissues or organs in the same area?

  • Where is it located?

The letter T is followed by a letter, number, or combination of letters after it. This gives additional information about the tumor. The different letters and numbers that may see include:

  • TX means that there is no information about the tumor or it cannot be measured.

  • T0 means that there is no evidence of a tumor.

  • Tis refers to a tumor in situ. This means that the tumor is only found in the cells where it started. It has not spread to any surrounding tissue.

T1-T4 describe the size and location of the tumor, on a scale of 1 to 4. A larger tumor or a tumor that has grown deeper into nearby tissue will get a higher number.

For some types of cancer, the T stage can be broken down into subcategories for even more detail. This is noted with a lowercase letter, like an a or b, such as T2b.

What these letters mean depends on the type of cancer. A lowercase m can also be used to show that there are multiple tumors.

Node (N)

The letter N and the number after it describe if cancer has affected the lymph nodes. The lymph nodes are small, bean-shaped organs that help fight infection.

They are a common spot where cancer first spreads. This part of the staging system answers these questions:

  • Has the tumor spread to the lymph nodes?

  • If so, which lymph nodes and how many?

Lymph nodes near where the cancer started are called regional lymph nodes. Lymph nodes in other parts of the body are called distant lymph nodes.

The N category only refers to lymph nodes near the cancer (regional lymph nodes). Distant lymph nodes elsewhere in the body are included in the M category (see below).

After the letter N, there will be a number from 0 (zero) to 3. N0 means there are no lymph nodes with cancer. Most often, the more lymph nodes with cancer, the larger the number.

But for some tumors, the location of the lymph nodes with cancer may determine the N category.

Metastasis (M)

The letter M and the number after it describes if the cancer has spread. It answers these questions:

  • Has the cancer spread to other parts of the body?

  • If so, where and how much?

  • If cancer has not spread, the stage is M0. If the cancer has spread to other parts of the body, it is stage M1.

Primary tumor (T)

  • TX: Main tumor cannot be measured.

  • T0: Main tumor cannot be found.

  • T1, T2, T3, T4: Refers to the size and/or extent of the main tumor. The higher the number after the T, the larger the tumor or the more it has grown into nearby tissues. T’s may be further divided to provide more detail, such as T3a and T3b.

Regional lymph nodes (N)

  • NX: Cancer in nearby lymph nodes cannot be measured.

  • N0: There is no cancer in nearby lymph nodes.

  • N1, N2, N3: Refers to the number and location of lymph nodes that contain cancer. The higher the number after the N, the more lymph nodes that contain cancer.

Distant metastasis (M)

  • MX: Metastasis cannot be measured.

  • M0: Cancer has not spread to other parts of the body.

  • M1: Cancer has spread to other parts of the body.

cancers staging tnm-staging

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