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About cancer stages

In order to prescribe treatment, doctors need to know the extent or “stage” of cancer in the body.  For breast cancer, the most common staging system is the “TNM” system. 

TNM stands for tumour, nodes and metastasis. These are measured as follows: 

  • Tumour: The size of the main tumour
  • Nodes: The number and location of any cancerous lymph nodes 
  • Metastasis: Determination as to whether or not the cancer has spread (metastasized) to other parts of the body

In breast cancer, there are five main stages: 0, I, II, III and IV. Generally, the possible outcome of the disease (prognosis) for the patient is better at lower stages. Very generally, the stages are: 

  • Stage 0: the cancer is only in the ducts, lobule or nipple and has not spread to nearby breast tissue and is at an early stage
  • Stage I: the tumour is less than 2 cm in diameter; the cancer has not spread to the lymph nodes or other parts of the body 
  • Stage II: A tumour larger than 2 cm but not more than 5 cm. Cancer may or may not have spread to the lymph nodes.
  • Stage III: A tumour of any size. Cancer has not spread to other parts of the body but is in the lymph nodes 
  • Stage IV: Cancer has spread to other parts of the body

Many of the tests used to diagnose cancer are also used to determine the cancer stage. 


Diagnostic tests Staging and other tests