Chapter 145 Breast: Cancer
INTRODUCTION
Description: Breast cancer is a malignant neoplasm of the breast classified by cell type, location, and degree of invasion. Breast cancer is the most common malignancy of women, accounting for almost one third of all women’s malignancies. Breast cancer accounts for approximately 18% of cancer deaths and results in about the same number of deaths per year as auto accidents.
Prevalence: Lifetime risk of 1 in 8 by age 90, >212,000 new cases, lifetime risk of death of 1 in 28, >40,000 deaths annually (2006). Roughly one new case of breast cancer is diagnosed every 3 minutes, and every 13 minutes there is a breast cancer death.
Genetics: Women with BRCA1 mutations have a 60% lifetime risk of breast cancer (BRCA2 mutations carry an 85% risk of breast cancer and up to 20% risk of ovarian cancer). Only 20% of patients with breast cancer have a family history of breast cancer. African-American women have a lower incidence of breast cancer (119.4/100,000 versus 141.1/100,000 for white women) but they have a higher mortality rate (34.7/100,000 versus 25.9/100,000).
ETIOLOGY AND PATHOGENESIS
Risk Factors: First-degree relative with breast cancer (relative risk [RR] = 2.3, RR = 10.5 with bilateral disease), moderate alcohol use (>3 to 5 drinks/day, RR = 1.41), early menarche, late menopause, nulliparity or late first pregnancy (>30 years), prior history of breast cancer (5%/year), estrogen use (RR = 1.12). Only 21% of patients with breast cancer age 30 to 54 years are identified by risk factors.
CLINICAL CHARACTERISTICS
DIAGNOSTIC APPROACH
Workup and Evaluation
Imaging: Mammography (detects 80% of all tumors), ultrasonography (may help to differentiate between solid and cystic masses), bone scan, and chest radiograph after diagnosis is established. Recent evidence suggests that for women with a lifetime risk that exceeds 20%, magnetic resonance imaging (MRI) screening may be beneficial. Digital radiography, thermal imaging (thermography), transillumination, mammoscintigraphy, ductography, and other techniques have not been shown to be comparable or superior to mammography.
Special Tests: Fine needle aspiration (FNA) of cells from a breast mass can provide histologic confirmation of malignancy and help direct definitive therapy.
