Breast Cancer Stages

“Breast cancer staging” refers to a standardized characterization of the different levels of disease development. Defining breast cancer stages allows medical professionals to effectively communicate with one another about a patient’s breast cancer. A breast cancer’s stage can be determined by the results of a physical exam, biopsy and imaging tests.

Breast Cancer StagesThe TNM Staging System

“TNM” stands for “tumor, nodes, metastases,” the cancer staging classification system of the American Joint Committee on Cancer and the International Union Against Cancer. This system may be applied to many types of cancer and helps establish a basis for breast cancer prognosis. The values ascribed to T, N and M are used to determine the stage of the cancer:

  • TX: Tumor cannot be measured/found
  • T0: No evidence of tumor
  • Tis: Tumor is “in situ,” meaning that it is localized
  • T1-T4: The higher the number, the larger and/or more invasive the tumor
  • NX: Nearby lymph nodes can’t be assessed
  • N0: Nearby lymph nodes aren’t affected
  • N1-N3: Lymph nodes are affected to varying degrees
  • MX: Metastasis (spread to other tissues and organs) can’t be measured/found
  • M0: Metastasis hasn’t occurred
  • M1: The cancer has spread to other tissues/organs.

Stages of Breast Cancer

Once the TMN values of a tumor have been assessed, the stage of the cancer can be determined. The stages are as follows:

  • Stage 0 refers to a non-invasive, non-metastasized cancerous tumor, which can often be successfully removed before it spreads.
  • Stage I cancer is invasive but the tumor is confined to the breast and less than two centimeters in diameter. Prognosis at this stage is often very good.
  • Stage II is characterized by a combination of tumor size and the distance the disease has spread. This stage is broken down into A and B sub-stages, but typically the cancer has spread to the nearby lymph nodes or armpit. The tumor is relatively small and the prognosis good.
  • Stage III is divided into three stages: IIIA, IIIB and IIIC. In this stage, the cancer has generally spread to the armpit, lymph nodes, chest wall, ribs, skin or muscles.
  • Stage IV breast cancer has spread to bones, lungs, liver, brain or other organs. Stage IV offers the lowest probability for survival of any of the stages.

Once a stage has been determined, the cancer is always referred to using that stage, even if the disease progresses. Someone diagnosed with Stage IIIA breast cancer will always be a Stage IIIA patient, even if the cancer metastasizes to another organ such as the lung. The cancer would then be called “Stage IIIA breast cancer with metastasis in the lungs.”


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