Breast Cancer Stages
There are two types of breast cancer stages. The anatomical stage describes how large the primary tumor is and how far the cancer has spread in your body. The prognostic stage predicts how you may respond to treatment. Both help doctors understand your disease and plan your care.
Anatomical stage
Breast cancer’s anatomical stage is based on how much cancer is in your body and where it is located.
Doctors can determine this through imaging exams, along with biopsy results and a physical examination; or through surgery.
Surgery is the more accurate method. For example, it could show the tumor is smaller than they originally thought, or that it has spread further than imaging tests showed.
Whether doctors use imaging exams or surgery, they will give you a TNM sage. The TNM stage describes cancer based on three factors:
- T: The size of the primary tumor (T) and whether it has invaded nearby tissue
- N: The cancer’s spread to nearby lymph nodes (N)
- M: Whether the cancer has spread, or metastasized (M), to distant parts of your body.
Each factor gets a number based on the extent of the cancer. Higher numbers indicate more advanced cancer. Tumors (T) are scored between 1-4, nodes (N) 1-3 and metastasis (M) 0-1.
The TNM stage can be simplified to stages 0-4. Stage 0 is the least advanced cancer. Stage 4 is the most advanced.
Prognostic stage
A newer staging system is the prognostic stage. The prognostic stage predicts how you may respond to treatment and the chance that your cancer comes back after a successful treatment.
The prognostic stage combines TNM staging with the cancer’s grade and molecular subtype. These provide information about the cancer’s cells and/or tissue.
Breast cancer grade
A cancer’s grade describes how cancer tissue and cells look under a microscope compared to healthy cells.
Cancers can be either low, intermediate or high grade. Low grade cancers are typically the least aggressive; high grade cancers are the most aggressive.
People with low-grade cancers have cancer cells and tissue that look very similar to healthy tissue. Doctors describe these cancers as well differentiated.
High-grade cancers have cells and tissues that look very abnormal compared to healthy tissue. These are also called poorly differentiated cancers.
Doctors determine breast cancer’s grade based on three factors:
- How much of the tumor tissue has normal breast ducts. Ducts transport milk to the nipple.
- The nuclei of tumor cells. Nuclei control activity in the cell. Larger, more misshapen nuclei are signs of an aggressive cancer.
- How many dividing cells are present. This indicates how fast the cancer cells are growing and dividing.
Each factor is given a score of 1-3, with higher scores meaning the cells and tissue look or behave more abnormally. The scores are then added to determine the cancer’s grade:
- 3 to 5: Grade 1 (Low grade or well differentiated)
- 6 to 7: Grade 2 (Intermediate grade or moderately differentiated)
- 8 to 9: Grade 3 (High grade or poorly differentiated)
Molecular subtype
Another factor in determining the prognostic stage is its molecular receptor status.
Receptors are molecules produced on or inside cancer cells by the cells themselves. They interact or bind with specific proteins and hormones in your body. This is called recognition.
There are three main receptors that can fuel the growth and spread of breast cancer. These receptors are also targets for cancer treatment, so they can impact your treatment plan and prognosis.
The receptors are:
- HER2 (Human epidermal growth factor receptor 2), a protein involved in cell growth.
- Estrogen receptors. Estrogen is a female sex hormone.
- Progesterone receptors. Progesterone is also a female sex hormone.
If a cancer tests negative for all three receptors, it is called triple-negative breast cancer.
Learn more about breast cancer's molecular subtypes.
0-4 prognostic stage
Once doctors know a breast cancer’s TNM stage, grade and molecular receptor status, they can determine the 0-4 prognostic stage.
For instance, a breast cancer that is T2, N2, M0; is grade 2; and tests negative for all three molecular receptors is stage III. If that same tumor tests positive for all three molecular receptors, it is only stage I.
Talk to your care team about your prognostic stage and what that stage means for your treatment and prognosis.