Staging provides a common way of describing the cancer, so doctors can work together to plan the best treatments.

TNM staging system

TNM  is the most common tool used by doctors to describe the stage of cancers.. Doctors use the results from diagnostic tests and scans to answer these questions:

1. Tumor (T): How large is the primary tumor in the breast? What are its biomarkers?
   
2. Node (N): Has the tumor spread to the lymph nodes? If so, where, what size, and how many?
   
3. Metastasis (M): Has the cancer spread to other parts of the body?
   

The results are combined to determine the stage of cancer for each person.

There are 5 stages of breast cancer: 

stage 0 (zero), which is non-invasive ductal carcinoma in situ (DCIS),

stages I through IV (1 through 4), which are used for invasive breast cancer. 

Staging can be clinical or pathological. 

Clinical staging is based on the results of tests done before surgery, which may include physical examinations, mammogram, ultrasound, and MRI scans. 

Pathological staging is based on what is found during surgery to remove breast tissue and lymph nodes. The results are usually available several days after surgery. In general, pathological staging provides the most information to determine a patient’s prognosis, and treatment options to be chosen

The first question many patients are keen on getting an answer to is the exact stage of the cancer. 

If you have surgery as the first treatment for your cancer, your doctor will generally confirm the stage of the cancer when the testing after surgery is finalized, usually about one to two weeks after surgery.

 When systemic treatment is given before surgery, which is typically with medications and is called neoadjuvant therapy, the stage of the cancer is primarily determined clinically. 

Doctors may refer to stage I to stage IIA cancer as “early stage” and stage IIB to stage III as “locally advanced.”

staging

Stage 0: Stage zero (0) describes disease that is only in the ducts of the breast tissue and has not spread to the surrounding tissue of the breast. It is also called non-invasive or in situ cancer (Tis, N0, M0).

Stage IA: 

The tumor is small, invasive, and has not spread to the lymph nodes (T1, N0, M0).

Stage IB: 

Cancer has spread to the lymph nodes and the cancer in the lymph node is larger than 0.2 mm but less than 2 mm in size. 

Or there is either no evidence of a tumor in the breast or the tumor in the breast is 20 mm or smaller 

Stage IIA: 

Any 1 of these conditions:

There is no evidence of a tumor in the breast, but the cancer has spread to 1 to 3 axillary lymph nodes. It has not spread to distant parts of the body.
The tumor is 20 mm or smaller and has spread to 1 to 3 axillary lymph nodes 

The tumor is larger than 20 mm but not larger than 50 mm and has not spread to the axillary lymph nodes (T2, N0, M0).

Stage IIB: Either of these conditions:

The tumor is larger than 20 mm but not larger than 50 mm and has spread to 1 to 3 axillary lymph nodes.

The tumor is larger than 50 mm but has not spread to the axillary lymph nodes (T3, N0, M0).

Stage IIIA: The cancer of any size has spread to 4 to 9 axillary lymph nodes or to internal mammary lymph nodes. It has not spread to other parts of the body 

(Stage IIIA may also be a tumor larger than 50 mm that has spread to 1 to 3 axillary lymph nodes 

Stage IIIB: 

The tumor has spread to the chest wall or caused swelling or ulceration of the breast, or it is diagnosed as inflammatory breast cancer. 

It may or may not have spread to up to 9 axillary or internal mammary lymph nodes. 

It has not spread to other parts of the body 

Stage IIIC: 

A tumor of any size that has spread to 10 or more axillary lymph nodes, the internal mammary lymph nodes, and/or the lymph nodes under the collarbone. 

It has not spread to other parts of the body.

Stage IV (metastatic): The tumor can be any size and has spread to other organs, such as the bones, lungs, brain, liver, distant lymph nodes, or chest wall.