Find out about the different staging systems for breast cancer and about breast cancer grading.
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 there are any cancer cells in the lymph nodes
- M describes whether the cancer has spread to a different part of the body
The number staging system divides breast cancers into 4 stages, from 1 to 4.
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 area of the breast after treatment.
Locally advanced breast cancer means the cancer hasn't spread to another part of the body but might be:
- bigger than 5 cm across
- growing into the skin or muscle of the chest
- present in the lymph nodes in the armpit, and the nodes are stuck to each other or to other structures
Secondary breast cancer is also called metastatic 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 means what the cancer cells look like under the microscope.
Breast cancers can be:
- low grade – grade 1 (slow growing)
- intermediate grade – grade 2
- high grade – grade 3 (faster growing)
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.
What differentiation means
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 to 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 its grade.
Well differentiated carcinomas have fairly normal looking cells that appear to be growing slowly. 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).
Poorly differentiated carcinomas have abnormal features, tend to grow and spread more quickly, and have a worse outlook (prognosis).
Moderately differentiated carcinomas have features and an outlook (prognosis) somewhere between well differentiated and poorly differentiated.