What is the TNM Breast Cancer Staging System?

By Dr. Kathleen Ruddy

The word stage usually refers to what extent something, say a process, has progressed. Breast cancer progresses in stages. Each stage describes what is happening to the body, and to what level the cancer has spread. During treatment of breast cancer, the stage of the cancer is one of the determining factors. The Tumor Node Metastasis (TNM) staging system is the standard used to measure breast cancer malignancy that has been in use for treatment of breast cancer.

How is Breast Cancer Staging Done?

The staging of breast cancer is performed by the use of imaging tests such as mammograms, computed tomography (CT) scans, chest x-rays, and magnetic resonance imaging (MRI). In addition to these, physical exams and biopsies also help doctors evaluate breast cancer stages. Lastly, blood tests are sometimes performed to indicate general health of the patient, as well as show if the cancer has spread to other parts of the body.

Who Came up With the TNM System?

The TNM staging system was developed more than 60 years ago by Pierre Denoix of France, but wasn’t applied to breast cancer until the late 1960s. After its introduction, the American Joint Committee on Cancer (AJCC) improved upon the first model and made it a standardized way for cancer doctors to evaluate the extent of the disease in patients.

A BRIEF HISTORY

The TNM system was developed between 1943 and 1952 by Pierre Denoix as a classification system for malignant tumors. In 1953, a World Health Organization Sub-Committee on Cancer Registration and Presentation agreed on the staging system, and since then has been adopted worldwide as the standard for describing and classifying cancer progression stages.

How is Breast Cancer Malignancy Classified?

By using the TNM staging system, breast cancer malignancy is classified according to the T, N, and M stages. The letter T takes into account the size of the cancerous tumor, N determines whether the cancer has affected the lymph nodes, and M indicates if the cancer has spread to other body organs. The letter T usually has a number in the 0-4 range that indicates the size of the tumor and how far it is under the breast. The letter N has a number in the 0-1 range that shows the number of lymph nodes affected, and M has 0 or 1 to show if body organs are affected.

How do They Fit Together?

The doctor will put the results of the TNM staging system together to give a picture of the cancer. For example, the doctor might put down the test results as T1 N0 M1. This means that there is a single tumor that is two centimeters across (T1), no evidence of the tumor in the lymph nodes (N0), and evidence that the cancer has spread to other body organs (M1).

Why is Staging Important?

Staging breast cancer using the TNM system is important because it helps the doctor give the right treatment options. If the cancer tumor is deemed to be localized to one area, then local treatment options such as surgery or radiotherapy may be enough to take eradicate it. If the cancer has spread to other parts of the body, local treatment may not be an option, and options such as drug treatments and chemotherapy are considered.

Do Other Forms of Cancer Have Similar Staging Systems?

Yes, they do. Most types of cancer have their form of staging system that is sometimes similar to the TNM staging system. In all cases, the staging systems help doctors describe the magnitude of the tumor, and what treatment options are available for each stage. The other common staging system is the Number System.

The TNM staging system is periodically revised to keep up with advancement in medical technology and treatment. However, such changes are kept to a minimum to allow the system to be relied upon by medical practitioners. A patient’s outcome can’t be predicted in any way. However, with the TNM staging system, breast cancer malignancy is kept in check, and the data collected helps with the treatment decision.

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