Breast Cancer: Complete Guide
Quick Facts
- Most common cancer in women worldwide
- 1 in 8 women will develop breast cancer in their lifetime
- Early detection significantly improves outcomes
- 5-year survival rate for localized breast cancer is 99%
- Multiple treatment options available based on type and stage
What is Breast Cancer?
Breast cancer is a disease in which cells in the breast grow out of control. It can begin in different parts of the breast, including the ducts, lobules, or tissue in between. While breast cancer occurs primarily in women, men can also develop this disease.
Key Points
- Breast cancer is not a single disease but a group of diseases
- Different types require different treatment approaches
- Early detection through screening saves lives
- Treatment is more effective when cancer is found early
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.
Types of Breast Cancer
Non-Invasive Types
- Ductal Carcinoma In Situ (DCIS): Abnormal cells confined to milk ducts
- Lobular Carcinoma In Situ (LCIS): Abnormal cells in lobules, considered a risk factor
Invasive Types
- Invasive Ductal Carcinoma (IDC): Most common type (70-80% of cases)
- Invasive Lobular Carcinoma (ILC): Second most common (10-15% of cases)
- Triple-Negative Breast Cancer: Lacks ER, PR, and HER2 receptors
- HER2-Positive Breast Cancer: Overexpresses HER2 protein
- Inflammatory Breast Cancer: Rare, aggressive form
Molecular Subtypes
Based on hormone receptor status and HER2 status:
- Luminal A (ER+/PR+, HER2-, low Ki-67)
- Luminal B (ER+/PR+, HER2+ or high Ki-67)
- HER2-enriched (ER-, PR-, HER2+)
- Basal-like (Triple negative)
Signs and Symptoms
Common Symptoms
- New lump in breast or underarm
- Thickening or swelling of part of the breast
- Irritation or dimpling of breast skin
- Redness or flaky skin in nipple area
- Nipple discharge other than breast milk
- Change in size or shape of breast
- Pain in any area of the breast
⚠️ When to See a Doctor
Contact your healthcare provider immediately if you notice:
- A new, hard lump or thickening in your breast
- Bloody nipple discharge
- Sudden breast skin changes
- Inverted nipple (if new)
Causes and Risk Factors
Non-Modifiable Risk Factors
- Age: Risk increases with age
- Genetic mutations: BRCA1, BRCA2, and other genes
- Family history: First-degree relatives with breast cancer
- Personal history: Previous breast cancer or certain benign conditions
- Dense breast tissue: Makes detection harder
- Early menstruation: Before age 12
- Late menopause: After age 55
Modifiable Risk Factors
- Physical inactivity
- Obesity after menopause
- Hormone replacement therapy
- Alcohol consumption
- Reproductive history (no pregnancies or first pregnancy after 30)
Diagnosis
Screening Methods
- Mammography: X-ray of the breast, gold standard for screening
- Clinical breast exam: Physical examination by healthcare provider
- Breast self-exam: Optional, helps with breast awareness
Diagnostic Tests
- Diagnostic mammography: Detailed X-ray
- Breast ultrasound: Uses sound waves
- Breast MRI: Detailed imaging using magnets
- Biopsy: Tissue sample for definitive diagnosis
- Fine-needle aspiration
- Core needle biopsy
- Vacuum-assisted biopsy
- Surgical biopsy
Biomarker Testing
Tests performed on tumor tissue:
- Estrogen receptor (ER) status
- Progesterone receptor (PR) status
- HER2 status
- Ki-67 (proliferation marker)
- Oncotype DX (21-gene test)
Staging
Breast cancer staging uses the TNM system and is grouped into stages 0-IV:
| Stage | Description | 5-Year Survival Rate |
|---|---|---|
| Stage 0 | DCIS - non-invasive, confined to ducts | ~100% |
| Stage I | Small tumor (≤2cm), no lymph nodes or micrometastases | ~100% |
| Stage II | Larger tumor and/or spread to few lymph nodes | 93% |
| Stage III | Locally advanced, multiple lymph nodes involved | 72% |
| Stage IV | Metastatic - spread to distant organs | 22% |
Treatment Options
Local Treatments
Surgery
- Lumpectomy: Removes tumor and small margin of tissue
- Mastectomy: Removes entire breast
- Sentinel node biopsy: Checks first lymph nodes
- Axillary dissection: Removes multiple lymph nodes
Radiation Therapy
- External beam radiation
- Brachytherapy (internal radiation)
- Intraoperative radiation
Systemic Treatments
Chemotherapy
Common regimens include:
- AC-T (Adriamycin, Cytoxan, Taxol)
- TC (Taxotere, Cytoxan)
- CMF (Cytoxan, Methotrexate, 5-FU)
Hormone Therapy
For ER/PR positive cancers:
- Tamoxifen
- Aromatase inhibitors (Letrozole, Anastrozole, Exemestane)
- Ovarian suppression
Targeted Therapy
For HER2-positive cancers:
- Trastuzumab (Herceptin)
- Pertuzumab (Perjeta)
- T-DM1 (Kadcyla)
- Tucatinib (Tukysa)
Immunotherapy
- Pembrolizumab (Keytruda) for triple-negative
- Atezolizumab (Tecentriq)
Prognosis and Survival Rates
Prognosis depends on multiple factors:
- Stage at diagnosis
- Tumor grade
- Hormone receptor status
- HER2 status
- Patient age and overall health
- Response to treatment
Overall Statistics
- 5-year relative survival rate: 90%
- 10-year relative survival rate: 84%
- Localized disease: 99% 5-year survival
- Regional spread: 86% 5-year survival
- Distant metastasis: 29% 5-year survival
Prevention
Risk Reduction Strategies
- Maintain healthy weight
- Exercise regularly (150 minutes/week)
- Limit alcohol consumption
- Avoid smoking
- Breastfeed if possible
- Limit hormone therapy
For High-Risk Individuals
- Enhanced screening (MRI + mammography)
- Chemoprevention (Tamoxifen, Raloxifene)
- Prophylactic surgery (for BRCA carriers)
- Genetic counseling and testing
Living with Breast Cancer
During Treatment
- Managing side effects
- Nutrition and exercise
- Emotional support
- Work and financial planning
After Treatment
- Follow-up care schedule
- Surveillance for recurrence
- Managing long-term side effects
- Healthy lifestyle maintenance
Frequently Asked Questions
Is breast cancer hereditary?
About 5-10% of breast cancers are hereditary, caused by inherited gene mutations like BRCA1 and BRCA2. Having a family history increases risk but doesn't guarantee developing cancer.
Can men get breast cancer?
Yes, though rare. About 1% of breast cancers occur in men. Risk factors include BRCA2 mutations, Klinefelter syndrome, and family history.
What age should screening start?
Guidelines vary. Most recommend starting mammograms at age 40-50 for average-risk women. High-risk individuals may start earlier with additional screening methods.
Does breast cancer always require chemotherapy?
No. Treatment depends on cancer type, stage, and molecular features. Some early-stage, hormone-positive cancers may be treated with surgery and hormone therapy alone.
What is the difference between DCIS and invasive breast cancer?
DCIS (Stage 0) is confined to milk ducts and hasn't spread. Invasive cancer has spread beyond ducts into surrounding breast tissue and potentially beyond.
Related Topics
Medical Disclaimer
This information is for educational purposes only and should not replace professional medical advice. Always consult with qualified healthcare providers for diagnosis and treatment decisions.
Sources
- National Cancer Institute. Breast Cancer Treatment (PDQ) - Health Professional Version. Updated January 2026.
- American Cancer Society. Breast Cancer Facts & Figures 2025-2026.
- NCCN Guidelines. Breast Cancer. Version 1.2026.
- Siegel RL, et al. Cancer Statistics, 2026. CA Cancer J Clin. 2026.
- ASCO Clinical Practice Guidelines. Breast Cancer. 2025.