Breast cancer is characterised by the malignant growth of epithelial cells of the breast ducts or lobules. Approximately 185,000 cases of breast cancer are diagnosed each year (in the US); there are 43,500 deaths, making breast cancer second to lung cancer as a leading cause of death by cancer among women. Incidence rates of breast cancer are rising (8.2% for white and 7% for black women in U.S.) in developed countries; mortality rates are stable. Breast cancer in men is uncommon (<1%). The different types of breast cancer include: lobular carcinoma in situ (LCIS), ductal carcinoma in situ (DCIS), invasive ductal carcinoma (70% to 80% of all breast cancers), Paget's disease of the nipple, inflammatory carcinoma, and other uncommon types. Women detect 90% of their breast cancers with breast self-examination (BSE). This early detection is associated with a more favourable clinical stage; it does not reduce mortality.

Aetiology / Risk Factors

• Increasing age
• History of cancer in one breast
• History of benign breast disease
• Nulliparity or first pregnancy after 30
• Family history (first-degree relative) of breast cancer (especially significant for premenopausal women)
• Early menarche and late menopause
• Long-term oral contraceptive or HRT use; this is controversial
• High doses of ionising radiation before age 35
• History of cancer of the colon, thyroid, endometrium, or ovary
• Diet high in animal fat, excessive alcohol consumption, and in some studies, obesity
• Inherited germline mutations (10% of cases) of the following genes: p53 (Li-Fraumeni syndrome), BRCA-1, and BRCA-2, and the ataxia-telangiectasia gene.
• History of breast implants

• Palpable lump
• Dimpled skin
• Striae and erythema
• Increased vascularity
• Enlarged axillary lymph nodes
• Yellow, clear, or bloody discharge from the nipple
• Breast pain and soreness (rare except in very advanced cases)