Breast cancer is a disease in which abnormal cells in breast tissue grow and multiply uncontrollably. It is one of the most common cancers affecting women, although men can also develop breast cancer. Early detection and advances in treatment have improved outcomes for many people. Advances in molecular testing and targeted treatment continue to change breast cancer care. At the same time, screening, healthy lifestyle habits, appropriate follow-up, and awareness of persistent breast changes remain important parts of breast health.
Breast cancer does not always cause noticeable symptoms in its early stages. Possible signs include:
Many breast changes are caused by noncancerous conditions, but a new or persistent change should be evaluated by a healthcare professional.
Breast cancer includes several different forms. The most common types begin in the ducts or lobules of the breast.
Invasive ductal carcinoma (IDC) begins in the milk ducts and can spread into surrounding breast tissue.
Invasive lobular carcinoma (ILC) begins in the milk-producing lobules and can have a different growth pattern from ductal cancer.
Other types include inflammatory breast cancer, Paget disease of the breast, and less common breast tumors.
Breast cancers are also classified according to the presence of certain receptors.
Hormone receptor-positive breast cancer has estrogen receptors, progesterone receptors, or both. Hormone therapy can be an important part of treatment.
HER2-positive breast cancer produces excessive amounts of the HER2 protein. Several targeted therapies are available for this subtype.
Triple-negative breast cancer does not have estrogen receptors, progesterone receptors, or excess HER2. Chemotherapy, immunotherapy, and other treatments may be considered depending on the specific situation.
Diagnosis often begins with breast imaging.
Depending on age, symptoms, and clinical findings, testing may include:
A biopsy is generally needed to confirm whether abnormal tissue contains cancer cells.
Laboratory testing of biopsy tissue can determine hormone receptor status, HER2 status, tumor characteristics, and other information that helps guide treatment.
After diagnosis, doctors determine the stage of the cancer.
Staging considers factors such as:
Breast cancer is commonly described from stage 0 through stage IV. Stage IV indicates that cancer has spread to distant parts of the body.
Treatment depends on the cancer's stage, subtype, receptor status, genetic characteristics, overall health, and previous treatment.
Surgery can involve removing the tumor while preserving much of the breast, known as breast-conserving surgery, or removing the entire breast through mastectomy.
Lymph nodes may also be evaluated or removed depending on the situation.
Radiation uses high-energy treatment to destroy cancer cells and reduce the risk of cancer returning in certain parts of the body.
It is frequently used after breast-conserving surgery and may also be recommended in selected cases after mastectomy.
Chemotherapy uses medicines that destroy or slow the growth of rapidly dividing cancer cells.
It may be given before surgery to shrink a tumor or after surgery to reduce the risk of recurrence.
For hormone receptor-positive breast cancer, medications can block hormonal signals that help cancer cells grow.
Common approaches include selective estrogen receptor modulators, aromatase inhibitors, and other endocrine treatments.
HER2-positive breast cancers may respond to targeted treatments that specifically interfere with HER2 signaling.
Several HER2-directed medicines are used depending on the stage and treatment setting.
Immunotherapy can be used for certain breast cancers, particularly selected cases of triple-negative breast cancer.
These medicines work by helping the immune system recognize and attack cancer cells.
Advances in molecular testing have led to treatments aimed at specific characteristics within cancer cells.
Targeted medicines may be used for particular mutations, receptors, or other tumor features.
Risk can be influenced by many factors, including:
Having a risk factor does not mean breast cancer will develop, and some people develop breast cancer without an identifiable major risk factor.
Breast cancer screening can help detect certain cancers before symptoms appear.
Mammography is a commonly used screening method, although recommendations regarding when to begin screening and how frequently to screen can vary based on age, risk factors, and national guidelines.
People with a strong family history or inherited cancer risk may require a different screening approach.
Some breast cancers are associated with inherited genetic changes, including variants in BRCA1 and BRCA2.
Genetic counseling and testing may be considered when there is a strong family history, early-onset breast cancer, certain tumor characteristics, or other factors associated with inherited risk.
Genetic information can sometimes influence treatment decisions and help assess cancer risk among relatives.
After treatment, ongoing medical follow-up is important.
Follow-up care may include physical examinations, mammography when appropriate, management of treatment side effects, physical activity, nutrition, and emotional support.
Some people experience long-term effects such as fatigue, nerve symptoms, menopausal changes, or arm swelling after lymph-node treatment. These issues can often be managed with appropriate supportive care.
Breast cancer is a complex group of diseases rather than a single condition. Differences in tumor type, stage, hormone receptors, HER2 status, and genetic characteristics can significantly influence treatment and prognosis.
Early detection through appropriate screening and prompt evaluation of concerning breast changes can improve the chance of finding cancer at a more treatable stage. Diagnosis generally involves imaging followed by a biopsy, with laboratory testing used to identify important characteristics of the tumor.
Modern treatment can involve surgery, radiation therapy, chemotherapy, hormone therapy, HER2-targeted medicines, immunotherapy, and other targeted treatments. Many patients receive a combination of therapies rather than a single treatment.
Treatment decisions are highly individualized. Factors such as cancer stage, tumor biology, overall health, genetic findings, and previous treatments all play a role in determining the most appropriate approach.