Understanding Your Breast Cancer Diagnosis
A breast cancer diagnosis is only the beginning of understanding the disease. Breast cancers are not all alike, and several features help determine how serious the cancer is and which treatments are most likely to work.
The most important include the type, stage, grade, hormone-receptor status, HER2 status, lymph-node involvement, and sometimes genomic and inherited genetic testing.
Two women can both have “breast cancer” yet have very different cancers and treatment choices.
What Type of Breast Cancer Is It?
One of the first questions is where the cancer began and whether it has invaded surrounding breast tissue.
Ductal carcinoma in situ (DCIS) consists of abnormal cells confined within a milk duct and is often called Stage 0 breast cancer. It is not invasive, but some DCIS can eventually become invasive. Doctors cannot always predict which cases will progress, raising concerns about overdiagnosis and overtreatment.
Invasive ductal carcinoma (IDC) begins in a milk duct and has spread into surrounding breast tissue. It is the most common invasive breast cancer.
Invasive lobular carcinoma (ILC) begins in the milk-producing lobules and has invaded surrounding tissue. It can sometimes be more difficult to detect on mammography.
Whether a cancer is ductal or lobular, in situ or invasive, is important—but its other biological characteristics may have an even greater influence on treatment.
Stage and Grade: How Serious Is It?
Stage and grade describe different things.
Stage describes how much cancer is present and how far it has spread. Breast cancer ranges from Stage 0 to Stage IV.
Stage 0: Usually DCIS, confined within the milk ducts.
Stages I and II: Generally cancer confined to the breast or with limited nearby involvement.
Stage III: More extensive involvement of the breast, nearby tissues, or lymph nodes, without distant spread.
Stage IV: Metastatic breast cancer that has spread to distant organs such as the bones, liver, lungs, or brain.
Grade describes how abnormal the cancer cells look under a microscope. Grade 1 cancers generally grow more slowly; Grade 3 cancers tend to behave more aggressively; Grade 2 falls between them.
Put simply, stage tells us primarily where the cancer is; grade gives clues about how it may behave.
Hormone Receptors and HER2
Breast cancer cells are tested for proteins that can help them grow because these results can determine which treatments are most likely to work.
Estrogen receptor (ER) and progesterone receptor (PR): Hormone-receptor-positive cancers may respond to treatments that block estrogen or reduce its production.
HER2: HER2-positive cancers produce excess HER2 protein. Highly effective HER2-targeted drugs have substantially improved treatment for these cancers.
These tests divide breast cancers into several important groups:
Hormone-receptor positive, HER2-negative: The most common group; hormone therapy is often important.
HER2-positive: Can often be treated with HER2-targeted drugs.
Triple-negative: Lacks ER, PR, and excess HER2. Chemotherapy remains important, while immunotherapy and newer targeted treatments are options for some patients.
These differences help explain why cancers of the same size and stage may require very different treatments.
Have the Lymph Nodes Been Involved?
Breast cancer can spread to nearby lymph nodes, particularly those under the arm. Their involvement helps determine stage and treatment.
During surgery, doctors may perform a sentinel lymph node biopsy, removing a small number of the first nodes to which the cancer would be expected to spread.
If these nodes are cancer-free, more extensive lymph-node surgery can often be avoided. Even when cancer is found, removing many additional nodes is not always necessary.
Importantly, cancer in nearby lymph nodes does not mean Stage IV breast cancer. Stage IV means cancer has spread to distant parts of the body.
Avoiding unnecessary lymph-node removal can reduce the risk of lymphedema and shoulder problems.
Genomic Tests: Can Chemotherapy Be Avoided?
For some early breast cancers, a genomic test can help determine whether chemotherapy is likely to provide additional benefit.
One of the most widely used is Oncotype DX, which examines the activity of 21 genes within the cancer and produces a Recurrence Score.
It is used mainly for certain hormone-receptor-positive, HER2-negative early breast cancers. Large studies have shown that many women in this group can be treated without chemotherapy, while women with higher-risk results may benefit from it.
The score is considered along with age, menopausal status, lymph-node involvement, tumor size, and grade.
Should You Have Inherited Genetic Testing?
Genomic tumor testing is different from testing for inherited genetic mutations.
The best-known inherited mutations are BRCA1 and BRCA2, although PALB2, CHEK2, ATM, and other genes can also increase breast cancer risk.
Testing may be particularly important depending on age at diagnosis, type of breast cancer, family history, and other personal risk factors.
The results can affect:
Treatment: Some cancers associated with BRCA mutations may respond to PARP inhibitors.
Future risk: Certain mutations can increase the risk of another breast cancer or other cancers and may influence surgery and screening decisions.
Family members: A positive result may provide important information for children, siblings, and other relatives.
Because genetic testing has become increasingly complex, genetic counseling can be helpful in deciding what to test and understanding the results.
Most breast cancers are not caused by an inherited mutation.
Questions to Ask Your Doctor
Exactly what type of breast cancer do I have?
What is the stage and grade?
What are my ER, PR, and HER2 results?
Are any lymph nodes involved?
Has the cancer spread beyond the breast and nearby lymph nodes?
Would a genomic test such as Oncotype DX help determine whether I need chemotherapy?
Should I have inherited genetic testing?
How quickly do I need to make a treatment decision?
Would a second opinion or pathology review be useful?
Learn More
An overview of the tests used to diagnose breast cancer and determine its characteristics.
Clear explanations of pathology reports, breast cancer types, grade, stage, hormone receptors, and HER2 status.
Explains inherited cancer mutations, who may benefit from genetic testing, and the role of genetic counseling.
Information about the genomic test used to help determine whether chemotherapy may benefit certain women with early-stage, hormone-receptor-positive, HER2-negative breast cancer.
An independent patient-advocacy perspective on breast cancer screening, diagnosis, and treatment, with attention to the evidence, benefits, harms, and areas of controversy.
Video
An explanation of the TNM staging system—tumor size, lymph-node involvement, and metastasis—and how this information helps determine breast cancer stage.