Staging: Understanding Your Breast Tumor Size

The TNM staging system

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doctor explaining mammogram results to patient
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At some point in your cancer journey, especially after you've had a breast biopsy, lumpectomy, or mastectomy you'll be told the stage of your cancer. It's important for you to understand your stage because it's related to treatment options and survival rates.

One of the first questions you may ask is, "Has 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 TNM System for Breast Cancer Staging

The most widely used staging system is the TNM system.

T = Tumor Size 

From imaging tests (usually mammogram or ultrasound), radiologists can measure your tumor's size. That size is divided into four classes:

  • T-1: 0 - 2 centimeters
  • T-2: 2 - 5 cm
  • T-3: greater than 5cm
  • T-4: tumor of any size that has broken through (ulcerated) the skin or is attached to the chest wall

N = 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 to the tumor tested for cancer and micro-metastasis.

The two ways to check the lymph nodes are 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. 

  • N-0 = the surgeon cannot feel any swollen nodes
  • N-1 = the surgeon can feel some swelling and thinks the nodes are positive (cancerous)
  • N-2 = the lymph nodes feel like they are quite swollen, lumpy, and bunched together
  • N-3 = swollen lymph nodes are near the collarbone

The second way to evaluate lymph nodes is with a sentinel node biopsy.

M = Metastasis

Metastasis affects the stage of cancer.

  • M-0 = a sample of the nodes have been surgically removed and tested and are clear of cancer
  • M-1 = nodes have cancer cells or micrometastasis in them; The tumor has shed cells beyond its original location, and that cancer may be in other parts of the body

All of the TNM information will be combined twice, once by the surgeon, and again by the pathologist in the lab. Each expert will give an opinion about your case in terms of its TNM stage. Neither of these opinions will be the exact answer to "what stage is this cancer?" You may need to know more about it, such as:

All of these factors affect your diagnosis and will be heavily considered when you and your doctor look at treatment options.

The Stages of Breast Cancer

Breast cancer has four stages, and if pre-cancerous conditions are included, a fifth. Your stage depends on the tumor's TNM rating.

Stage 0 (Precancer)

Stage zero is used for precancerous, or in situ, carcinomas. In this stage, there's no evidence that abnormal cells have broken out of the area where they originated or invading neighboring tissues.

Stage 1

Stage 1 means it's invasive cancer (cells are moving into surrounding tissues.) Stage 1 has two subcategories:

In Stage 1A:

  • The tumor measures up to 2 centimeters
  • AND cancer cells have not spread out of the breast into the lymph nodes

In Stage 1B:

  • A small group of cancer cells measuring between 0.2 millimeters and 2 millimeters is found in the lymph nodes
  • A stage 1A tumor may or may not exist

Stage 2

Stage 2 is for cancer that has become invasive. This stage also is divided into A and B subcategories.

In Stage 2A:

  • No tumor is in the breast, but cancer larger than 2 millimeters is present in lymph nodes, either axillary (under the arm) or near the breast bone
  • OR the tumor is smaller than 2 centimeters and has spread to the lymph nodes
  • OR the tumor measures between 2 and 5 centimeters and hasn't spread to the lymph nodes
  • Under certain conditions, tumors of this size may still be classified as Stage 1

Stage 2B:

  • Tumor measures between 2 and 5 centimeters and small groups of cells (between 0.2 and 2 millimeters) exist in the lymph nodes
  • Tumor measuring 2-5 cm plus cancer in up to three lymph nodes
  • Tumor measures larger than 5 cm but isn't in the axillary lymph nodes

Stage 3

Stage 3 cancers are invasive This stage is divided into three subcategories.

Stage 3A:

  • Breast tumor of any size (or no tumor) and cancer in between four and nine lymph nodes
  • OR tumor larger than 5 cm and small groups of cancer cells (0.2 mm-2 mm) in the lymph nodes
  • OR tumor larger than 5 cm and cancer has spread to up to three lymph nodes
  • Under certain conditions, tumors of this size may be classified as 1B

Stage 3B:

  • Tumor of any size that has spread to the chest wall and/or skin and causes swelling or an ulcer
  • AND may have spread to up to nine axillary lymph nodes or may have spread to lymph nodes near the breast bone
  • OR fits the criteria for inflammatory breast cancer (skin on the breast is red and may feel warm or be swollen, and cancer has spread to the lymph nodes and possibly the skin)
  • Under certain circumstances, tumors meeting the first two criteria may be classified as stage 2A

Stage 3C:

  • No tumor or a tumor of any size that has spread to the chest wall and/or skin
  • AND cancer that's spread to 10 or more axillary lymph nodes
  • OR has spread to lymph nodes above or below the collarbone
  • OR has spread to lymph nodes near the breastbone
  • Under certain circumstances, tumors meeting the above criteria may be classified as stage 3A

Stage 4

Stage 4 is also called metastatic breast cancer. Rather than being confined to the breast and nearby lymph nodes, it's traveled to other organs. Common metastases sites include the lungs, skin, bones, liver, brain, or distant lymph nodes.

It may also be a recurrence of breast cancer that has spread to other areas.

How Tumor Size Is Measured

Tumor sizes are measured by a radiologist using a mammogram or an ultrasound image of your breast. However, not all tumors are simple, round shapes that are easy to measure.

For example, the tumor could be elongated like a baked potato and the image could be at an angle that makes it hard to see all of the dimensions. Some tumors even have irregular edges that make it hard to estimate the total diameter.

Getting a Good Image

It takes time to gather all the details about your cancer, but with each step, you get an increasingly clear picture. To measure the size of your tumor before surgery, doctors rely on imaging studies. Standard breast imaging methods include:

  • Mammogram: Traditional film mammography can be used to image breast tissue, but is less accurate on dense breast tissue. If you are pre-menopausal or have never been pregnant, your breasts may be dense enough to hide masses, making them harder to measure. Digital mammography works very well on dense breast tissue, though. If you are post-menopausal, have fatty breast tissue, or have been pregnant, film mammography may be accurate enough. 
  • Breast Ultrasound: Ultrasound is great for distinguishing between a fluid-filled cyst and a dense mass that's more likely to be a tumor. Ultrasound can be used to make a measurement of a breast tumor, as well, but it may be slightly less accurate than a mammogram, as it has been found to underestimate tumor size. Elastography is a promising new technique that combines ultrasound with compression to detect tumors, which are much more rigid and unyielding than healthy breast tissue and other kinds of masses.
  • Breast MRI: MRI is noninvasive and painless, and uses no radiation to create a series of images of your breast tissue. While a mammogram may find your lump, an MRI might be needed to measure it if your breast tissue is dense or your biopsy shows that the mass is larger than expected. MRI can also be used during neoadjuvant chemotherapy to monitor the progress of treatment. While MRI can create a clear image of your tumor, it tends to over-estimate the actual size in three dimensions.

    Surgical Pathology Results

    Biopsies and imaging studies give an approximate measurement of your tumor, but you need the actual tumor size in order to make the best treatment decisions. Your surgeon will use the information from previous tests as guidance when removing your tumor.

    After a lumpectomy or mastectomy, your excised breast tissue will be combined with your biopsy tissue, and a pathologist will examine the actual mass. The pathological measurement of your tumor is the gold standard for tumor size. Your post-surgical pathology report will summarize your comprehensive diagnosis of breast cancer.

    Reasons for Conservative Surgery

    Because the post-surgery pathology report is the best way to find out your tumor size, you may be asking, "Why not just do surgery and skip all these other tests?" That answer is: Because your biopsy and imaging studies are done in order to guide you and your surgeon in making the most conservative choice for breast surgery.

    If a lumpectomy will remove your cancer, you may be able to avoid a mastectomy. If neoadjuvant chemo may shrink your tumor before surgery, then you may need less tissue removed in a lumpectomy. However, in some cases, such as widely scattered invasive breast cancer, a mastectomy might be the only surgical option. Having the most information and understanding the implications of your tests helps you make informed, intelligent treatment decisions.

    A Word From Verywell

    When you plan a doctor visit and you know that you will be discussing your diagnosis, lab results, or treatment plans, you may want to ask someone to come along with you, to take notes. If that's not possible, you may want to record the appointment on your phone or a small tape recorder. The shock of unpleasant news can make it hard to take in the rest of the conversation. Having someone you trust with you can really help, both so you aren't relying on your own memory alone and to help you get through it emotionally.

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