Breast cancer size

1. How big is the cancer?
2. Does cancer size affect outcome? 
3. More than one area of cancer
4. What is residual size?
5. How size affects treatment options 

1. How big is the cancer?

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). One inch equals about 25mm or 2.5 centimetres (cm). 

A pathology report will show:

• The size of the invasive cancer – breast cancer that has the potential to spread 
• 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 ‘whole tumour size’.

2. Does cancer size affect outcome?

Only details of the invasive breast cancer will be used by your treatment team to look at your prognosis (outlook).  

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

A small cancer can be fast growing while a larger cancer may be slow growing, or it could be the other way around.  

3. More than one area of cancer

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

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

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

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

4. What is residual size?

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

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

How much breast cancer is still there will indicate the response to the treatment you had before surgery. This is called the pathological response:

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

5. How size affects treatment options 

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. 

If you have a larger cancer in relation to your breast size, your treatment team may recommend a mastectomy to remove all the breast tissue. Or they may suggest chemotherapy to try to shrink the cancer before surgery.

With smaller cancers it’s often possible to have breast-conserving surgery, also called wide local excision or lumpectomy. This is where only the cancer and a margin (border) of normal breast tissue surrounding it are removed.

Your treatment team will decide whether to 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.  

Generally, people with breast cancers greater than 2cm are more likely to be offered chemotherapy. This is because larger cancers may have been there longer before being found and so may have had more chance to spread.