Breast Tumor Size and Staging

Staging breast cancer and looking at lymph node involvement are essential for your oncology team to determine the extent of disease, treatment options, and prognosis.

Your oncologist likely uses the TNM staging system, developed by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC), to conclude how these characteristics define a case of breast cancer.

You will be told the stage of your breast cancer usually at the start of your cancer journey, especially after you've had a breast biopsy, lumpectomy (surgical removal of the tumor), or mastectomy (surgical removal of the breast).

This article will discuss the TNM staging system and its role in helping to diagnosis cancer stage and lymph node involvement.

The TNM System for Breast Cancer Staging

TNM is the most widely used staging system for breast cancer. Each letter of the acronym stands for a defining element of the disease.

"T" for Tumor Size 

To measure the size of your tumor before surgery, healthcare providers rely on imaging studies.

Standard breast imaging methods include:

• Mammogram: Traditional film mammography can be used to image breast tissue. If you are postmenopausal, have fatty breast tissue, or have been pregnant, this may be accurate enough. If you have dense breast tissue, digital mammography is more reliable.
• Breast ultrasound: Ultrasound can be used to make a measurement of a breast tumor, but it has been found to underestimate tumor size and is considered less accurate than mammography.
• Breast MRI: Although a mammogram may find your lump, an MRI (magnetic resonance imaging) might be needed to measure it if your breast tissue is dense or your biopsy shows that the mass is larger than expected. However, while MRI can create a clear image of your tumor, it tends to overestimate the actual size in three dimensions.

After reviewing imaging studies, radiologists can approximate your tumor's size. Not all tumors are simple, round shapes. 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.

Size is divided into four classes in the TNM system:

"N" for Lymph Node Status

Since cancer can travel through your body in your lymph system, it is important to have the lymph nodes that are nearest to your tumor tested for cancer and micrometastases (small collection of cancer cells that are shed from the original tumor and travel through blood or the lymph system).

Your surgeon may check your lymph nodes by palpating (feeling) the skin just above the lymph nodes and rating what they notice.

Alternatively, your lymph nodes may be evaluated via a sentinel node biopsy (procedure that determines when the cancer has spread into your lymph system).

"M" for Metastasis

Metastasis, the extent to which the cancer has spread, also affects the stage of cancer.

Putting It All Together

All of the TNM information will be combined twice, once by the surgeon and again by the pathologist (the specialist who is trained in diagnosing body tissues and fluids). Each expert will give an opinion about your case in terms of its TNM stage. To officially determine the breast cancer stage, your team may need to know more about:

• Hormone receptor status (tells you whether you have receptors for the hormones estrogen and progesterone)
• Grade of the tumor (speed of growth)
• Where in your body the cancer has traveled to (if it has metastasized)

The Stages of Breast Cancer

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

Stage 0 (Precancer)

Stage 0 is used for precancerous, or in situ, carcinomas. In this stage, there's no evidence that abnormal cells have traveled from the area where they originated or are invading neighboring tissues.

Stage 1

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

Stage 1A:

• The tumor measures up to 2 cm.
  AND
• Cancer cells have not spread out of the breast into the lymph nodes.

Stage 1B:

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

Stage 2

Stage 2 is cancer that has become invasive. This stage also is divided into A and B subcategories, as follows:

Stage 2A:

• No tumor is in the breast, but cancer larger than 2 mm is present in lymph nodes, either axillary (under the arm) or near the breastbone.
  OR
• The tumor is smaller than 2 cm and has spread to the lymph nodes.
  OR
• The tumor measures between 2 cm and 5 cm and hasn't spread to the lymph nodes.

Under certain conditions, tumors of this size may still be classified as stage 1.

Stage 2B:

• The tumor measures between 2 cm and 5 cm and small groups of cells (between 0.2 mm and 2 mm) exist in the axillary lymph nodes.
  OR
• The tumor measures 2–5 cm and there is cancer in up to three axillary lymph nodes.
  OR
• The 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, as follows:

Stage 3A:

• Any size breast tumor (or no tumor) is present and cancer has been found in between four and nine lymph nodes.
  OR
• The tumor is larger than 5 cm and small groups of cancer cells (0.2–2 mm) are in the lymph nodes.
  OR
• The tumor is 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:

• A tumor of any size has spread to the chest wall and/or skin and caused swelling or an ulcer.
  AND
• Cancer may have spread to up to nine axillary lymph nodes or may have spread to lymph nodes near the breastbone.
  OR
• The case 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:

• A tumor of any size has spread to the chest wall and/or skin.
  AND
• Cancer has spread to 10 or more axillary lymph nodes.
  OR
• Cancer has spread to lymph nodes above or below the collarbone.
  OR
• Cancer 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 sites of metastases include the lungs, skin, bones, liver, brain, and distant lymph nodes.

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

Tumor Size and Next Steps

Biopsies (removing a sample of tissue for testing in a lab) 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.

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

With that in mind, it may seem counterintuitive to rely on the tumor size estimations used in TNM staging. But there is good reason for this: Imaging allows you and your surgeon to make the most conservative choice when it comes to breast surgery. Your surgeon will use the information from previous tests as guidance when removing your tumor.

If a lumpectomy will remove your cancer, you may be able to avoid a mastectomy. If neoadjuvant chemo is used to shrink the 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.

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Summary

Getting an accurate diagnosis is important to making decisions about chemotherapy, surgery, and radiation if you have breast cancer. Your oncologist likely uses the TNM staging system, which is the standard system in the United States to determine the severity of disease, evaluate lymph node involvement, and make an overall assessment of your prognosis.

A Word From Verywell

When you and your healthcare provider 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 take notes on a notepad.

News of any diagnosis often comes with a lot of information, medical terminology, and emotions. Having something you can refer back to can help if you leave your appointment and details are fuzzy.