Breast Cancer Staging

Written by Robert Goldstein | Published on September 8, 2014
Medically Reviewed by Kenneth R. Hirsch, MD on September 8, 2014

Breast Cancer Diagnosis & Staging

Lumps in the breast, or changes in breast shape, size, or skin qualities can be caused by many different conditions.

A positive breast cancer diagnosis can only be achieved through an examination of breast tissue. Biopsies play a critical role in breast cancer diagnoses. To understand diagnoses, you should understand the stages of breast cancer and what each means for overall outlook. Make note of all your symptoms and communicate clearly with your doctor about how your body is feeling.

Breast Cancer Staging

Breast cancer must be staged before a diagnosis can be complete and a treatment course chosen. The process determines whether cancer has spread from the breast to other parts of the body. The most commonly used system is the American Joint Committee on Cancer TNM system. In the TNM staging system, cancers are classified based on their T, N, and M stages:

  • T indicates the size of the tumor and how far it has spread within the breast and to nearby organs.
  • N stands for how much it has spread to lymph nodes.
  • M defines metastasis, or how much it has spread to distant organs.

In TNM staging, each letter is associated with a number to explain how far the cancer has progressed. Once the TNM staging has been determined, this information is combined into a process called “stage grouping.” Stage grouping is the common staging method, in which stages range from 0 to 4. The lower the number, the earlier the cancer stage.

Stage 0

This stage describes noninvasive (“in situ”) breast cancer. Ductal carcinoma in situ (DCIS) is an example of stage 0 cancer.

Stage 1

These breast cancers are subdivided into two categories (1A and 1B) based on a number of criteria.

This stage marks the first identification of invasive breast cancer. At this point, the tumor measures no more than 2 centimeters in diameter (or about 3/4 inch). Stage 1 breast cancer is divided into stages 1A and 1B.

Stage 1A means that the tumor is 2 centimeters or smaller, and that the cancer hasn’t spread anywhere outside the breast.

Stage 1B means that small clusters of breast cancer cells are found in the lymph nodes. Typically at this stage, either no discrete tumor is found in the breast or the tumor is 2 centimeters or smaller.

Stage 2

This stage describes invasive breast cancers in which one of the following is true: 

  • The tumor measures less than 2 centimeters (3/4 inch), but has spread to lymph nodes under the arm.
  • The tumor is between 2 and 5 centimeters (about 3/4 inch to 2 inches) and may or may not have spread to lymph nodes under the arm.
  • The tumor is larger than 5 centimeters (2 inches), but hasn't spread to any lymph nodes.
  • No discrete tumor is found in the breast, but breast cancer larger than 2 millimeters is found in 1-3 lymph nodes under the arm or near the breastbone.

Stage 2 breast cancer is divided into stage 2A and 2B.

In stage 2A, no tumor is found in the breast or the tumor is smaller than 2 centimeters. Cancer may be found in the lymph nodes at this point. Or the tumor is larger than 2 centimeters but smaller than 5 centimeters and the cancer has not spread to the lymph nodes.

In stage 2B, the tumor may be larger than 2 centimeters, smaller than 5 centimeters, and breast cancer cells are found in the lymph nodes. Or the tumor may also be larger than 5 centimeters, but cancer hasn’t spread to the lymph nodes.

Stage 3

By definition, stage 3 cancers have not spread to distant sites.

  • Stage 3A tumors are either larger than 5 centimeters (2 inches) and have spread to one to three lymph nodes under the arm, or are any size and have spread into multiple lymph nodes.
  • stage 3B tumor of any size has spread to tissues near the breast — the skin and chest muscles — and may have spread to lymph nodes within the breast or under the arm.
  • Stage 3C cancer is a tumor of any size that has spread: 
    • to 10 or more lymph nodes under the arm
    • to lymph nodes above or beneath the collarbone and near the neck on the same side of the body as the affected breast
    • to lymph nodes within the breast itself and under the arm

Stage 4

Stage 4 breast cancer has spread to distant parts of the body, such as the lungs, liver, bones, or brain. At this stage, cancer is advanced and curative treatment options are very limited.

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