Breast cancer
Breast cancer is a malignancy of ductal or lobular epithelium, most often presenting as a firm, painless mass in the upper outer quadrant. Diagnosis rests on core needle biopsy with estrogen, progesterone, and HER2 receptor testing, and first-line treatment pairs breast-conserving surgery or mastectomy with sentinel node biopsy, radiation, and receptor-guided systemic therapy such as tamoxifen or trastuzumab.
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What this article covers
- Overview
Breast cancer is a malignancy of mammary ductal or lobular epithelium progressing from atypical hyperplasia through carcinoma in situ to invasive disease with lymphatic and hematogenous spread.
- Epidemiology
Breast cancer is diagnosed in about 268,600 US women annually, developing in roughly 1 in 8 women (12.4% lifetime risk), and causes an estimated 40,610 deaths yearly.
- Risk factors
Age and sex: risk rises continuously after age 40; female sex alone accounts for most risk.
- Pathophysiology
Sporadic breast cancer accumulates genetic change stepwise: normal epithelium progresses through atypical hyperplasia to carcinoma in situ (ductal, DCIS, or lobular, LCIS), then invasive carcinoma…
- Clinical features
Early, localized disease: a single, nontender, firm-to-hard, immobile mass with ill-defined margins, most often upper outer quadrant, or an asymptomatic mammographic finding.
- Differential diagnosis
Fibroadenoma: well-circumscribed, mobile, rubbery mass most common at ages 15 to 35, unchanged by the menstrual cycle, unlike cancer's fixed, hard mass.
- Diagnosis
Diagnosis is first established by core needle biopsy showing invasive carcinoma, with estrogen receptor (ER), progesterone receptor (PR), and HER2 testing on the same specimen; fine needle aspiration…
- Management
First-line locoregional therapy for stage 0 to III disease is breast-conserving surgery with sentinel node biopsy for a tumor 5 cm or smaller without skin or chest-wall involvement, then whole-breast radiation.
- Complications
Lymphedema: arm swelling after axillary dissection or nodal radiation, months to years later, with a lifelong cellulitis risk; sentinel biopsy carries a much lower risk than full dissection.
- Prognosis
Five-year relative survival tracks stage: 100% for stage 0, 98.9% for localized disease, 85.7% for regional (node-positive) disease, and 28.1% for distant metastatic disease.
- Prevention
Average-risk screening: mammography every 1 to 2 years starting at age 40 to 50, continued while life expectancy exceeds 10 years; a symptomatic finding warrants imaging at any age.
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