Overview
Breast cancer is a disease in which malignant cells form in the tissues of the breast. It is the second most common cancer among women in the United States, though it can also occur in men. Breast cancer begins when cells in the breast start to grow out of control, forming a tumor that can often be seen on an x-ray or felt as a lump.
The breast is made up of three main parts: lobules (glands that produce milk), ducts (tubes that carry milk to the nipple), and connective tissue. Most breast cancers begin in the ducts or lobules. Breast cancer can spread outside the breast through blood vessels and lymph vessels, a process called metastasis.
Early detection through regular screening and advances in treatment have significantly improved outcomes for people with breast cancer. The 5-year survival rate for localized breast cancer is now over 99%, highlighting the importance of early diagnosis and treatment.
Symptoms
Breast cancer symptoms can vary significantly between individuals. Some people may have no symptoms at all in the early stages. Regular screening is crucial because breast cancer is easier to treat when detected early.
Lump or Mass in Breast
The most common symptom is a new lump or mass. A painless, hard mass with irregular edges is more likely to be cancerous, but breast cancers can also be soft, round, tender, or even painful.
Nipple Discharge or Bleeding
Spontaneous discharge from the nipple, especially if it's bloody or occurs in only one breast, can be a warning sign of breast cancer.
Breast Pain or Soreness
While breast pain is more commonly associated with benign conditions, persistent pain in one area of the breast can sometimes indicate cancer.
Changes in Breast Appearance
This includes swelling of all or part of the breast, skin dimpling, nipple retraction (turning inward), or redness, scaliness, or thickening of the nipple or breast skin.
Lymph Node Changes
Swelling or lumps in the lymph nodes under the arm or around the collarbone may indicate that breast cancer has spread.
Important: Many of these symptoms can also be caused by benign breast conditions. However, if you notice any changes in your breasts, it's important to see a healthcare provider promptly for evaluation.
Causes
Breast cancer occurs when some breast cells begin to grow abnormally. These cells divide more rapidly than healthy cells and continue to accumulate, forming a lump or mass. The exact cause of breast cancer is not fully understood, but researchers have identified factors that increase risk.
Cellular Changes
Breast cancer results from mutations in the DNA of breast cells. These genetic changes can be:
- Inherited: About 5-10% of breast cancers are hereditary, caused by abnormal genes passed from parent to child
- Acquired: Most DNA changes related to breast cancer occur during a person's lifetime
Hormonal Influences
Hormones, particularly estrogen and progesterone, play a significant role in breast cancer development. Prolonged exposure to these hormones can increase risk, which is why factors like early menstruation, late menopause, and hormone replacement therapy are associated with higher breast cancer risk.
Environmental Factors
Various environmental and lifestyle factors may contribute to breast cancer development, including radiation exposure, certain chemicals, obesity, alcohol consumption, and lack of physical activity.
Risk Factors
Several factors can increase the risk of developing breast cancer. Having one or more risk factors doesn't mean you will definitely develop breast cancer; many people with risk factors never develop the disease.
Non-modifiable Risk Factors
- Gender: Women are about 100 times more likely to develop breast cancer than men
- Age: Risk increases with age; most breast cancers are diagnosed after age 50
- Genetic mutations: Inherited changes to BRCA1 and BRCA2 genes significantly increase risk
- Family history: Having close relatives with breast cancer increases risk
- Personal history: Previous breast cancer or certain benign breast diseases
- Dense breast tissue: Makes tumors harder to detect and slightly increases risk
- Early menstruation or late menopause: Longer lifetime exposure to hormones
Modifiable Risk Factors
- Physical inactivity: Lack of regular exercise
- Overweight or obesity: Especially after menopause
- Alcohol consumption: Risk increases with amount consumed
- Hormone therapy: Combined hormone therapy for menopause
- Reproductive history: Not having children or first pregnancy after age 30
- Not breastfeeding: Breastfeeding may slightly lower risk
- Radiation exposure: Previous radiation therapy to the chest
Types of Breast Cancer
There are several types of breast cancer, classified based on where they start and whether they have spread:
Non-invasive (In Situ)
- Ductal Carcinoma In Situ (DCIS): Abnormal cells confined to the milk ducts. Considered Stage 0 breast cancer
- Lobular Carcinoma In Situ (LCIS): Abnormal cells in the lobules. Not true cancer but increases risk
Invasive Breast Cancers
- Invasive Ductal Carcinoma (IDC): Most common type (70-80% of cases). Starts in ducts and spreads to surrounding tissue
- Invasive Lobular Carcinoma (ILC): Second most common (10-15%). Starts in lobules and can spread
- Triple-negative breast cancer: Lacks estrogen, progesterone, and HER2 receptors. More aggressive
- HER2-positive breast cancer: Has excess HER2 protein. Tends to grow faster
- Inflammatory breast cancer: Rare but aggressive. Causes breast to appear swollen and red
Less Common Types
- Paget's disease of the nipple
- Phyllodes tumors
- Angiosarcoma
- Male breast cancer
Diagnosis
Breast cancer diagnosis involves several steps and may include various tests to confirm the presence of cancer and determine its characteristics.
Screening Methods
- Mammography: X-ray of the breast, the most common screening tool
- Clinical breast exam: Physical examination by a healthcare provider
- Breast self-exam: Personal awareness of breast changes
Diagnostic Tests
- Diagnostic mammography: More detailed X-rays when abnormality is found
- Breast ultrasound: Uses sound waves to evaluate lumps or abnormalities
- Breast MRI: Detailed images using magnetic fields
- Biopsy: Removal of tissue sample for testing. Types include:
- Fine-needle aspiration
- Core needle biopsy
- Surgical biopsy
Laboratory Tests
If cancer is found, additional tests determine its characteristics:
- Hormone receptor testing: Checks for estrogen and progesterone receptors
- HER2 testing: Determines if cancer overproduces HER2 protein
- Genetic testing: May check for BRCA mutations or other genetic markers
- Oncotype DX: Analyzes genes to predict recurrence risk
Staging
Staging describes the extent of cancer in the body and helps determine treatment options and prognosis. The TNM system is commonly used:
TNM Classification
- T (Tumor): Size and extent of the main tumor
- N (Nodes): Whether cancer has spread to nearby lymph nodes
- M (Metastasis): Whether cancer has spread to other parts of the body
Stage Groupings
- Stage 0
- Non-invasive cancer (DCIS or LCIS)
- Stage I
- Small tumor (≤2 cm) with no lymph node involvement
- Stage II
- Larger tumor (2-5 cm) and/or involvement of nearby lymph nodes
- Stage III
- Locally advanced cancer with extensive lymph node involvement
- Stage IV
- Metastatic cancer that has spread to distant organs
Treatment Options
Breast cancer treatment depends on the type and stage of cancer, as well as individual factors. Most people receive a combination of treatments.
Surgery
- Lumpectomy: Removes tumor and small margin of surrounding tissue
- Mastectomy: Removes all or part of the breast
- Total (simple) mastectomy
- Modified radical mastectomy
- Skin-sparing or nipple-sparing mastectomy
- Lymph node surgery: Sentinel node biopsy or axillary dissection
- Reconstruction: Can be done immediately or delayed
Radiation Therapy
Uses high-energy rays to kill cancer cells. Types include:
- External beam radiation
- Brachytherapy (internal radiation)
- Intraoperative radiation
Systemic Treatments
Clinical Trials
Research studies testing new treatments may offer access to cutting-edge therapies.
Prevention
While not all breast cancers can be prevented, several strategies can help reduce risk:
Lifestyle Modifications
- Maintain healthy weight: Especially important after menopause
- Stay physically active: Aim for at least 150 minutes of moderate exercise weekly
- Limit alcohol: No more than one drink per day
- Don't smoke: Smoking increases risk of many cancers
- Breastfeed if possible: Longer duration provides more protection
- Limit hormone therapy: Use lowest dose for shortest time if needed
Screening Guidelines
Follow recommended screening guidelines based on your risk level:
- Average risk: Annual mammograms starting at age 40-45
- High risk: May need earlier or additional screening (MRI)
- Genetic counseling: Consider if strong family history
Preventive Medications
For high-risk individuals, options include:
- Tamoxifen or raloxifene for risk reduction
- Aromatase inhibitors for postmenopausal women
Preventive Surgery
For very high-risk individuals (BRCA mutations), prophylactic mastectomy or oophorectomy may be considered.
When to See a Doctor
Schedule an appointment with your healthcare provider if you notice:
- A new lump or mass in your breast or underarm
- Changes in breast size, shape, or appearance
- Dimpling, puckering, or bulging of the skin
- Nipple changes, including inversion or discharge
- Redness, scaliness, or thickening of breast skin
- Breast pain that doesn't go away
Seek immediate care if you have:
- Sudden onset of breast inflammation with fever
- Rapidly growing mass or skin changes
- Signs of infection after breast surgery
Medical Disclaimer: This information is for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for diagnosis and treatment of any medical condition.