You may come across a staging system for breast cancer. This is a way of summarising all of the information about a particular cancer.
There are different staging schemes in use. A common scheme is the Number Staging System such as that used by Cancer Research UK:
Stage 0: This is used to describe preinvasive cancer (sometimes called precancerous change). There is no evidence that the cells can spread beyond the breast.
Stage I: An invasive cancer up to 2 cm across with no evidence of spread.
Stage II: Stage II is divided into IIa and IIb.
Stage IIa.An invasive cancer less than 2cm where there are cancer cells in the armpit gland, but the glands are not stuck together OR A cancer that is less than 5cm where no lymph glands are involved OR Where there are cancer cells in the armpit nodes, but the nodes are not stuck together, but there is no cancer to be found in the breast (it is occult).
Stage IIb.The cancer is less than 5cm, the armpit glands contain cancer cells but the glands are not stuck together and the cancer had not spread any further OR The cancer is bigger than 5cm with no cells in the armpit glands and the cancer had not spread.
Stage III: Stage III is divided into IIIa, IIIb and IIIc.
Stage IIIa.is where there are cancer cells in the lymph glands and the glands are stick together, but there is no cancer to be found in the breast, OR The tumour is smaller than 5cm and the armpit glands contain cancer cells that are stuck together, but there is no evidence of any further spread, OR The cancer is larger than 5cm and the armpit glands contain cancer cells and may be stuck together, but there is no sign of any further spread
Stage IIIb.The cancer is fixed to the skin or chest wall, the lymph nodes may or may not contain cancer, but there is no further spread
Stage IIIc.The cancer can be any size and has spread to lymph nodes in the armpit and under the breast bone, or to nodes above or below the collarbone, but there is no further spread
Stage IV: A cancer of any size where cancer has spread to other parts of the body, for example the liver or lungs. The lymph nodes may or may not be involved.
The YNM system considers the tumour (T), the lymph nodes (N) and the presence of any distant spread (or metastases, M).