In most cases the cause of breast cancer is unknown. In a small percentage of cases, it is caused by a defective gene. Other potential causes or risk factors may include:
It’s too early to know for sure what causes breast cancer or whether they affect breast cancer risk.
Some of the ways to help reduce the risk of developing breast cancer include:
The US Preventive Services Task Force (USPSTF) recommends screening with mammograms every 2 years for women between the ages of 50 and 74 years. The American Cancer Society (ACS) recommends starting earlier and more frequently with yearly screening between 45 and 54 years. Screening can/should start at earlier ages if there are risk factors.
Breast cancer evaluation should start with symptoms, a comprehensive clinical history, and an evaluation of risk factors. This is followed by a sequence that has become formalized as triple assessment:1
There are several different types of breast cancer, based on where in the breast the cancer develops. Breast cancer can also be classified based on the types of cells involved. The 4 most common subtypes of breast cancer are called luminal A, luminal B, triple negative, and HER2 type.
HR stands for hormone receptor. HR+ means that tumor cells have receptors for the hormones estrogen or progesterone, which can promote the growth of HR+ tumors. HER2 stands for human epidermal growth factor receptor 2. HER2+ means that tumor cells make high levels of a protein called HER2/neu, which has been shown to be associated with certain aggressive types of breast cancer.1 Tumors classified as HR+/HER2− include those that are HER2-low and are the most common subtype, accounting for around 70% of all breast cancers.2
Generally, the sooner you can start treatment, the better. That being said, you do not need to rush into treatment immediately. Other factors may be at play such as additional testing and analyses. Your doctor may recommend starting treatment within a couple weeks or months of the diagnosis.
Like all types of cancer, breast cancer can potentially spread (metastasize) beyond the breast. In order for breast cancer to spread, cancerous cells must break away from the original tumor and attach to the wall of a lymph vessel or a blood vessel. After that, the cancer must penetrate the vessel wall so that it can flow with the blood or lymphatic fluid to reach a distant lymph node or organ.
In breast cancer cases, the sentinel lymph node (the lymph node closest to the original tumor) is often located in the underarm area. Once cancerous cells enter the bloodstream or lymphatic system, it can spread to distant tissues and organs. The areas most often affected by breast cancer metastasis are:
Depending on your type of breast cancer, current treatment may include 1, several, or all the following:
Cooper University Health Care. Frequently asked questions about breast cancer. https://www.cooperhealth.org/services/breast-cancer/faq.
Moffitt Cancer Center. Breast cancer FAQs. https://www.moffitt.org/cancers/breast-cancer/faqs/.
National Institutes of Health (NIH). Cancer stat facts: Female Breast cancer subtypes.  https://seer.cancer.gov/statfacts/html/breast-subtypes.html.
Pegram M, Pietras R, Dang CT, et al. Evolving perspectives on the treatment of HR+/HER2+ metastatic breast cancer. Ther Adv Med Oncol. 2023;15:17588359231187201.
Stony Brook Cancer Center. Frequently asked questions about breast cancer. https://cancer.stonybrookmedicine.edu/FAQsAboutBreastCancer.
