Staging of breast cancer

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Tumour size and spread

Doctors have developed a system to tell how advanced or serious a cancer is. It is called staging. It evaluates the size of the tumour, how aggressive the cancer cells look in the microscope, the number and location of cancerous lymph nodes, and whether the cancer has spread to other tissue or organs. Information collected in staging is used to determine the likely outcome of the disease and to develop a treatment plan.

Size is important because the smaller the tumour, the less likely it has spread beyond the breast and the better the chance for successful treatment. Small tumours are classified as two centimetres or less.

The spread of cancer is referred to as either local, regional, or distant. Local means that the spread of cancer is confined within the breast. Even if cancer is found in several places in the breast, it is still considered local. Regional means that cancer has spread to the lymph nodes, mainly to the axillary nodes under the arm. Distant means that cancer has spread to other parts of the body.

Determining lymph node status
Lymph node status is determined by a pathologist who examines any nodes under a microscope after they have been removed from the armpit during surgery. This procedure is called a standard axillary dissection and it is most often done during the surgery that removes a tumour from the breast. However it can be done as a separate procedure.

A new option for determining node status is a sentinel node biopsy in which only one to three nodes are removed. The sentinel node is the first lymph node draining from the breast. A dye or radioactive tracer is injected to determine which node is the sentinel node. A sentinel node biopsy has fewer side effects and studies have shown that the procedure can be an effective way to assess node status, especially when done by experienced surgeons.

If nodes contain cancer cells, they are called positive nodes and the pathologist counts the number of nodes with cancer and includes the number in a pathology report.

Staging cancer
The scale used to determine the stage of breast cancer is called TNM staging and ranges from stage 0 to stage IV. A higher stage indicates more severe cancer. This chart gives a summary of TNM staging. T represents the size of the tumour in the breast, N indicates lymph node status, and M indicates metastasis.

Stage

(T) Tumour Size

(N) Axillary Lymph Nodes

(M) Metastasis

0

Tiny cluster of cancer cells in a breast duct (in situ)

No spread

None

I

Up to 2cm

No spread

None

II

Smaller than 2cm

Has spread to the axillary lymph nodes

None

 

Between 2cm & 5cm

May or may not have spread to the axillary lymph nodes

None

 

Larger than 5cm

No spread

None

III

Any size

Has spread to multiple axillary lymph nodes so that the nodes become attached to each other

None

 

Larger than 5cm

Has spread to axillary lymph nodes

None

 

Any size but cells have spread to skin or chest wall

May or may not have spread to the axillary lymph nodes

None

 

Any size

Has spread to lymph nodes along breastbone and above/below collarbone

None

IV

Any size

May or may not have spread to the axillary lymph nodes


Has spread to other organs of the body or the skin and lymph nodes above the collarbone

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