Breast cancer size

The size of the breast cancer, along with other features of the cancer, can help your treatment team decide what treatment to offer you.

Cancer size is included in your pathology results. 

The size of the breast cancer is measured at its widest point, usually in millimetres (mm).

A pathology report will show:

• The size of any invasive breast cancer
• The size of any DCIS (ductal carcinoma in situ) – an early form of breast cancer

If invasive breast cancer and DCIS are found together, the results will tell you the combined size, called the whole tumour size. However, your treatment team will only use the details of the invasive breast cancer to look at treatment options and your prognosis (outlook).

While smaller cancers may have a better outlook, size does not always give the whole picture and is just one part of the overall results. 

Your pathology results usually say whether there’s only 1 area of cancer or more than 1 area.

If there’s more than 1 area of breast cancer, each area is measured separately.

If there’s more than 1 area of breast cancer in the same quarter of the breast, it may be called multi-focal.

If there’s more than 1 area of breast cancer in different quarters of the breast, it may be called multi-centric.

Sometimes chemotherapy or hormone therapy are given before surgery, for example to shrink a larger cancer.  

After surgery, the tissue removed is checked by a pathologist. Your pathology report will tell you the size of any cancer still present. This is sometimes called the residual size of the cancer.

The size of the breast cancer that’s left will help your treatment team see how well you responded to the treatment you had before surgery. This is called the pathological response. It can be described in 3 ways:

• Complete pathological response, meaning no remaining cancer 
• Partial response, meaning only some remaining cancer 
• No evidence of response, meaning the cancer is the same size or bigger than before the chemotherapy or hormone therapy

The size of the cancer in relation to your breast size, as well as its position in the breast, may affect what operation you’re offered. 

Your treatment team may recommend:

•  A mastectomy
• Breast-conserving surgery

Your treatment team may recommend chemotherapy depending on the size and other features of the breast cancer, and whether any cancer cells have spread to the lymph nodes under the arm.  

You may have chemotherapy before surgery to shrink a larger breast cancer.