Breast Cancer: Causes, Symptoms, and Screening
Overview
Breast cancer is an abnormal, uncontrolled growth of cells in breast tissue. It is the most common cancer among women in the United States, with the American Cancer Society estimating about 320,000 new invasive cases in 2026. It is also a leading cause of cancer death among women, with roughly 42,000 deaths expected. While rare, it can also affect men, with about 2,700 new cases and 530 deaths estimated. Thanks to advances in screening and treatment, the overall 5-year relative survival rate for breast cancer is about 91%, rising to more than 99% when detected at an early, localized stage.
Causes and risk factors
Several factors increase the risk of developing breast cancer:
- Hormonal factors: early puberty, late menopause, prolonged hormone replacement therapy, long-term oral contraceptive use
- Genetic factors: mutations in the BRCA1 and BRCA2 genes, family history of breast or ovarian cancer
- Lifestyle factors: excessive alcohol consumption, obesity after menopause, sedentary lifestyle, smoking
- Reproductive factors: never having given birth, first pregnancy at a later age, not breastfeeding
- Personal history of high-risk breast lesions (atypical hyperplasia, lobular carcinoma in situ)
Symptoms
Clinical signs of breast cancer, from most to least common, include:
- A painless lump or mass in the breast or underarm
- A change in breast shape or size
- Nipple retraction or a change in its shape
- Spontaneous nipple discharge, especially if bloody or one-sided
- Redness, swelling, or an orange-peel texture on the breast skin
- A sore or wound that doesn’t heal
- Persistent, localized breast pain (a later and less specific sign)
In advanced stages, unexplained fatigue, weight loss, or bone pain may appear.
Diagnosis
Diagnosis relies on several complementary exams:
- Mammography: the standard imaging exam, often supplemented with a breast ultrasound
- Breast MRI: for dense breasts, genetic predisposition, or staging workups
- Biopsy: a tissue sample is essential to confirm malignancy and characterize the tumor (hormone receptors, HER2 status, grade)
Staging workups (CT scan, bone scan) are performed depending on the stage.
Treatments
Care is multidisciplinary and personalized based on tumor type, stage, and biological characteristics:
- Surgery: lumpectomy (partial removal) or mastectomy (full removal), often combined with lymph node removal or the sentinel lymph node technique
- Radiation therapy: to the remaining breast tissue or lymph nodes after breast-conserving surgery, to reduce the risk of local recurrence
- Chemotherapy: given before (neoadjuvant) or after (adjuvant) surgery depending on the case; sometimes used for metastatic disease
- Hormone therapy: for tumors expressing estrogen or progesterone receptors (tamoxifen, aromatase inhibitors)
- Targeted therapies: trastuzumab (Herceptin) and other anti-HER2 drugs for HER2-positive tumors
- Immunotherapy: an emerging option for certain subtypes (triple-negative breast cancer)
Prevention
Several measures can help reduce risk or support early diagnosis:
- Follow current screening guidelines: the U.S. Preventive Services Task Force (USPSTF) recommends a mammogram every 2 years starting at age 40 through age 74. Under the Affordable Care Act, this screening is covered with no out-of-pocket cost by most health insurance plans.
- Engage in regular physical activity (at least 30 minutes a day)
- Limit alcohol consumption and avoid smoking
- Maintain a healthy weight, especially after menopause
- Breastfeed when possible
- Tell your doctor about any family history so you can get appropriate follow-up and, if needed, genetic testing
When should you see a doctor?
See a doctor promptly if you notice a breast lump, a change in the appearance of the breast or nipple, unusual discharge, or persistent redness. Any unexplained change, even without pain, deserves prompt medical attention.
Key takeaway: Breast cancer is the most common cancer among women in the United States, but it is highly treatable, and often curable, when caught early. Getting a mammogram every two years starting at age 40 remains the most effective preventive step.
Sources
- American Cancer Society, cancer statistics and patient guidance
- National Cancer Institute (NCI), official U.S. government cancer information
- U.S. Preventive Services Task Force, official screening recommendations
- MedlinePlus, U.S. National Library of Medicine health information