Stages of breast cancer

Stages of breast cancer

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Determining the stage of your breast cancer is fundamental for planning your treatment and understanding the most likely outcome. If you have been diagnosed with breast cancer, your doctor will decide what additional tests may be helpful to find out if the disease has spread outside the breast.

About Stages


  • The cancer stage — shown as a number from 0 to IV — is based on the size of the tumour and whether the cancer has spread to the lymph nodes.
  • To determine your cancer stage, your doctor will ask questions about your medical history, perform a careful physical examination and review all prior tests as well as the results from the biopsy of the tumour or suspected area.
  • Additional tests, such as X-rays and blood work, may be needed. In general, the stage isn't fully known until after the operation to remove the tumour in your breast, when a sample can be taken from the lymph nodes under your arm.
  • Breast cancer staging is complicated, and the classification system sometimes changes as doctors learn more about breast cancer.

Stages 0 to IV: What They Mean

Once the operation is complete, the surgeon can determine the stage of your cancer. Breast cancer stages range from 0 to IV, with many subcategories. Lower numbers indicate earlier stages of cancer, while higher numbers reflect a late-stage of cancer.


Stage 0


This stage describes non-invasive breast cancer. It hasn't spread within the breast or to other parts of the body


Stage I

This stage is an early stage of invasive breast cancer in which:

  • The tumour measures no more than 2 centimetres in diameter
  • No lymph nodes are involved — the cancer hasn't spread outside the breast

Stage II

This stage, subdivided into IIA and IIB, describes invasive breast cancers in which one of the following is true:

  • The tumour measures less than 2 cm but has spread to lymph nodes under the arm
  • No tumour is found in the breast but cancer is found in the axillary lymph nodes
  • The tumour is between 2 cm and 5 cm and may have spread to lymph nodes under the arm
  • The tumour is larger than 5 cm but hasn't spread to any lymph nodes

Stage III

Stage III breast cancers are subdivided into three categories — IIIA, IIIB and IIIC — based on a number of different criteria. By definition, stage III cancers haven't spread (metastasised) to distant sites.

For example, a stage IIIA tumour is larger than 5 cm and has spread to one to three lymph nodes under the arm. Other stage IIIA tumours may be any size and have spread into multiple lymph nodes. The lymph nodes clump together and attach to one another or to the surrounding tissue.

In stage IIIB breast cancer, a tumour 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 IIIB also includes inflammatory breast cancer, an uncommon but aggressive type of breast cancer.

Stage IIIC cancer is a tumour 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
  • To lymph nodes within the breast itself and to lymph nodes under the arm

Stage IV

Stage IV breast cancer has spread to other distant parts of the body, such as the lungs, liver, bones or brain.

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