EPIDEMIOLOGY

• Affects 1/9 women
• Accounts for 20% of cancer deaths in women

RISK FACTORS

• Geographic (U.S. > Japan)
• Family history (mother and sisters): Risk, ×2-×9
  • First degree relative with breast cancer increases risk 2-3×;
  • Familial breast carcinoma linked to a gene at 17q21 (brca-1)
• Risk increases with age
• Pregnancy (early pregnancy and lactation are protective)
  • Nulliparity: Risk, ×3;
  • Women who have their 1st child before 18 yr of age have one-third risk of women who have 1st child after age 30
• Menstrual history (early menarche-late menopause): Risk, ×2
• Removal of ovaries before age 35 reduces risk to one third
• Exogenous estrogen may increase risk, esp. in presence of fibrocystic disease; contraceptive use shows no change in risk
• Increased risk with exposure to radiation Obesity
• High lipid diet; moderate ethyl alcohol consumption
• Proliferative breast disease and hyperplasia: Risk, ×2
• Atypical hyperplasia: Risk, ×4
• Carcinoma in situ: Risk, ×8 (High-grade DCIS lesions progress to invasive carcinoma in approximately 40% of cases, and the progression of lower-grade lesions is probably in the range of 20%. Approximately 30% of LCIS will progress to invasive carcinoma.)
• Risk of carcinoma in contralateral breast of patients with invasive carcinoma is 5x risk of general population, reaching 25-50% for lobular carcinoma in situ
• Multicentricity more common in lobular vs. ductal