 Introduction/Background Breast cancer is the most common nonskin cancer diagnosis in women and is second only to lung cancer with respect to cancer deaths. Early detection of breast cancer from regular screening substantially reduces breast cancer mortality [1]. Because regular screening identifies tumors when they are smaller and with fewer nodal metastases, patients with screen-detected breast cancers are less likely to require mastectomy or chemotherapy, thereby also decreasing morbidity [2]. Breast cancer risk is frequently divided into 3 major categories: average, intermediate, and high risk. Numerous factors contribute to breast cancer risk, so no single method or definition is used to classify each woman into a specific risk category [3,4]. The use of validated statistical models based largely upon family history, which also incorporate additional risk factors, represents one mechanism to estimate risk. Currently, risk categories are most frequently defined by estimated lifetime risk; however, different time horizons, such as 5 or 10 year risk, may also be valuable for guideline development and informed decision-making [3]. Women at average risk are typically defined as those with <15% estimated lifetime risk for developing breast cancer, whereas intermediate-risk women are generally defined as those with a 15% to 20% estimated lifetime risk. The high-risk category typically includes women who have a >20 to 25% estimated lifetime risk: women who carry a deleterious genetic mutation that increases breast cancer risk, as well as untested first-degree relatives of patients with these mutations and women who have received radiation therapy to the thorax or upper abdomen at an early age (<30 years).
Female Breast Cancer Screening.  Introduction/Background Breast cancer is the most common nonskin cancer diagnosis in women and is second only to lung cancer with respect to cancer deaths. Early detection of breast cancer from regular screening substantially reduces breast cancer mortality [1]. Because regular screening identifies tumors when they are smaller and with fewer nodal metastases, patients with screen-detected breast cancers are less likely to require mastectomy or chemotherapy, thereby also decreasing morbidity [2]. Breast cancer risk is frequently divided into 3 major categories: average, intermediate, and high risk. Numerous factors contribute to breast cancer risk, so no single method or definition is used to classify each woman into a specific risk category [3,4]. The use of validated statistical models based largely upon family history, which also incorporate additional risk factors, represents one mechanism to estimate risk. Currently, risk categories are most frequently defined by estimated lifetime risk; however, different time horizons, such as 5 or 10 year risk, may also be valuable for guideline development and informed decision-making [3]. Women at average risk are typically defined as those with <15% estimated lifetime risk for developing breast cancer, whereas intermediate-risk women are generally defined as those with a 15% to 20% estimated lifetime risk. The high-risk category typically includes women who have a >20 to 25% estimated lifetime risk: women who carry a deleterious genetic mutation that increases breast cancer risk, as well as untested first-degree relatives of patients with these mutations and women who have received radiation therapy to the thorax or upper abdomen at an early age (<30 years).