Staging means how big the cancer is and whether it has spread. Grading means how abnormal the cancer cells look under a microscope.
Doctors use the stage and grade of a cancer to help them decide which treatment you need.
There are different systems used in the UK to stage breast cancer. The most common one is the TNM system. Another is the number staging system.
Your doctor might also talk about early, locally advanced or secondary breast cancer.
The TNM staging system stands for Tumour, Node, Metastasis.
- T describes the size of the tumour
- N describes whether the cancer has spread to the lymph nodes
- M describes whether the cancer has spread beyond the lymph nodes to a different part of the body
The number staging system divides breast cancers into 4 stages, from 1 to 4. These are invasive breast cancers. This means the cancer cells have grown through the lining of the ducts into the surrounding breast tissue.
Stage 0 is used for ductal carcinoma in situ (DCIS). It is a pre invasive breast cancer. The cancer cells are in breast ducts and have not started to spread into the surrounding breast tissue.
Stage 1 breast cancer means that the cancer is small and only in the breast tissue or it might be found in lymph nodes close to the breast.
This is an early stage breast cancer.
Stage 2 breast cancer means that the cancer is either in the breast or in the nearby lymph nodes or both.
This is an early stage breast cancer.
Stage 3 means that the cancer has spread from the breast to lymph nodes close to the breast or to the skin of the breast or to the chest wall.
This is also called locally advanced breast cancer.
Stage 4 breast cancer means that the cancer has spread to other parts of the body.
You may hear this called advanced cancer, secondary breast cancer, or metastatic breast cancer.
Early, locally advanced and secondary breast cancer
Early breast cancer means the cancer hasn't spread beyond the breast or the lymph nodes in the armpit on the same side of the body. So, the cancer hasn't spread to any other part of the body.
Local recurrence means cancer that has come back in the breast, the armpit, or the chest wall after treatment.
Locally advanced breast cancer means the cancer has spread into the surrounding area, such as the lymph nodes, the skin or chest muscle. But it has not spread to other parts of the body.
Secondary breast cancer is also called metastatic breast cancer, advanced breast cancer, or stage 4 breast cancer. It means that the cancer has spread to other parts of the body, such as the liver or bones.
Grade and differentiation
The grade describes how a cancer cell looks under the microscope and whether they are similar or very different to normal cells.
You might hear your doctor use the terms well differentiated, moderately differentiated, or poorly differentiated. A pathologist checks the cancer cells for features that can help predict how likely the cancer is to grow and spread. These include:
- the arrangement of the cells in relation to each other
- whether they form tubules (gland formation)
- how similar they look to normal breast cells (the nuclear grade)
- how many of the cells are dividing (the mitotic count)
These features taken together tell how differentiated the cancer is and the grade.
Low grade (grade 1) the cells look similar to normal breast cells and are slow growing. These are well differentiated cancers. They are arranged in small tubules for ductal cancer and cords for lobular cancer. These cancers tend to grow and spread slowly and have a good outlook (prognosis).
Intermediate grade (grade 2) the cells look quite different to normal breast cells. They are moderately differentiated. This means the features and outlook (prognosis) are somewhere between well and poorly differentiated.
High grade (grade 3) the cells look very different to normal breast cells and are faster growing, these are poorly differentiated cancers that have abnormal features. They tend to grow and spread more quickly and have a worse outlook (prognosis).
Low grade cancers tend to grow more slowly than high grade. High grade cancers are more likely to come back after they have first been treated. But the grade can only give a guide to how any individual cancer will behave and individual cancers may behave differently.