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Stages of Breast Cancer - The TNM System

Staging Affects Treatment Options

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Updated June 26, 2014

If you've had a breast biopsy, lumpectomy, or mastectomy done and gotten back the results from the pathology lab, you will want to understand what the staging part of the report means to you. Staging is related to treatment options and survival rates.

One of the first questions you may ask is, "Has the cancer spread beyond the tumor, or is it all in one place?" Right now, there is not one simple test that gives you the answer to that question. But there is a system of categorizing cancer into stages, based on three factors. The staging system most widely used is the TNM system.

  • T is used for Tumor Size. In the image (mammogram or ultrasound) of the tumor, the radiologist can make a measurement of the tumor's size. Sometime this is hard to do, depending on the angle of the tumor in relation to the image film, or if the tumor is deep inside the breast. A tumor has indistinct, or irregular outer edges, sometimes called a spiculated shape. They aren't always round, and they can be longer than they are wide. The most accurate way to get the size of a tumor is to surgically remove all of it, and then measure it. Tumor Size is divided into four classes: T-1 is from 0 - 2 centimeters, T-2 is from 2 - 5 cm, T-3 is greater than 5cm, and T-4 is a tumor of any size that has broken through (ulcerated) the skin, or is attached to the chest wall.

  • N is used for Lymph Node status. Since cancer can travel through your body in your lymph system, it is important to have your lymph nodes that are nearest the tumor tested for cancer and micro-metastasis. There are two ways to check the lymph nodes: by touch, and by surgery. If your lymph nodes are checked by touch, your surgeon will palpate (feel) the skin just above the lymph nodes, and rate them. If the surgeon cannot feel any swollen nodes, the rating is N-0, if the surgeon can feel some swelling and thinks the nodes are negative (not cancerous) the rating is N-1a, and if the nodes are swollen and appear positive (cancerous) the rating is N-1b. If the lymph nodes feel like they are quite swollen and bunched together (rather lumpy), they are rated N-2, or if they are near the collarbone, they are rated N-3. The second way to evaluate lymph nodes is with a sentinel node biopsy.

  • M is used for Metastasis. Metastasis affects the stage of cancer. If a sample of the nodes have been surgically removed and tested, and are clear of cancer, they are rated M-0, but if they have cancer cells or micrometastasis in them, they are rated M-1. This tells you that the tumor has shed cells beyond its original location, and that cancer may be in other parts of the body.

How does all this relate to staging? Read more on page 2.
See a comparison table showing the relationship between TNM and Stages

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