ARTICLE

Breast cancer is the second leading cause of cancer death among women in the United States. Approximately 215 000 women were diagnosed with invasive breast cancer, 50 000 women were diag-nosed with ductal carcinoma in situ, and 40 000 women died of invasive breast cancer in 2005 (1). Worldwide, it is estimated that more than 1 million women are diagnosed with breast cancer every year, and more than 410 000 will die of the disease (2). Tobacco, one of the most widely examined environmental factors, contains human carcinogens and may contribute to a woman’s risk of devel-oping breast cancer (3). Epidemiological cohort studies with large numbers of participants in the United States and Japan have indi-cated that breast cancer risk is associated with active and passive smoking (4,5). Cigarette smoke is a complex mixture of more than 4000 chemical constituents. On average, approximately 1.0 mg (range 0.3–2.0 mg) of nicotine is absorbed systemically during th