Risk factors for breast cancer are important to consider when reading mammograms because they indicate a pretest probability of breast cancer. Compiling risk information on a breast history sheet or compiled by the technologist on a computerized form provides interpreting radiologists quick access to this important
information (Fig. 2.1). Breast cancer risk factors are listed in Box 2.1. The most important risk factors are personal or family history of breast cancer/ovarian cancer, genetic mutations predisposing to breast cancer such as BRCA 1/2, older age, and female gender.
Men also develop breast cancer, but only 1% of all breast cancers occur in men in the United States.
Breast cancer risk increases with increasing age and drops off at 80 years old. Women with a personal history of breast cancer have a higher risk of developing breast cancer in the ipsilateral or contralateral breast than does the general population. After breast cancer surgery, the conservatively treated breast has a 1% per year risk of developing recurrent or new cancer.
Breast cancer risk assessment uses breast cancer risk assess- ment models based on a detailed family history of breast or ovar- ian cancer looking for genetic predispositions for breast cancer, and calculates lifetime risks for breast cancer. The BRCAPRO, BOADICEA, modified Gail model, and Tyrer–Cuzick model take into account the age, number, and cancer types in affected rela- tives, as well as other risk factors, to estimate a lifetime risk for breast cancer. Both the NCCN and ACS consider a >20% to 25%
lifetime risk to be high risk. Women with a first-degree relative (mother, daughter, or sister) with breast cancer have approxi- mately double the risk of the general population and are at par- ticularly high risk if the cancer was premenopausal or bilateral.
If many relatives had breast or ovarian cancer, the woman may be a carrier of BRCA1 or BRCA2, the autosomal dominant breast cancer susceptibility genes. Genetic testing is most appropriately performed by genetic counseling professionals who evaluate, counsel, and support women because of untoward social effects of either positive or negative results. Carriers of the breast can- cer susceptibility gene BRCA1 on chromosome 17 have a breast cancer risk of 85% and an ovarian cancer risk of 63% by age 70. Women with BRCA2 on chromosome 15 have a high risk
Mammogram Analysis and Interpretation
Debra M. Ikeda and Kanae K. Miyake
CHAPTER OUTLINE
BREAST CANCER RISK FACTORS
SIGNS AND SYMPTOMS OF BREAST CANCER THE NORMAL MAMMOGRAM
Anatomy and Image Contrast
Breast Density, Breast Density Notification Legislation, and Breast Density Classification Based on the Breast Imaging Reporting and Data System
MAMMOGRAPHIC FINDINGS OF BREAST CANCER DISPLAY OF MAMMOGRAMS
Optimization of Reading Room and Image Display First Look at Two-Dimensional Views and Older Studies Systematic Search on Each Mammographic Two-
Dimensional View and Tomosynthesis LOCATION OF A FINDING
Location Description Based on BI-RADS 2013 Keys to Identify the Location of a Finding
SYSTEMATIC APPROACH TO MAMMOGRAPHY INTERPRETATION
Before Reading Mammogram
Systematic Approach to Interpretation of Mammogram REPORTING OF MAMMOGRAPHIC FINDINGS BASED
ON BI-RADS 2013
DIAGNOSTIC MAMMOGRAPHY
Diagnostic versus Screening Mammography
Additional Two-Dimensional Mammographic Views and Tomosynthesis
DIAGNOSTIC LIMITATIONS
Breast Cancer Missed by Mammography KEY ELEMENTS
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of breast cancer and a low risk of ovarian cancer. These genes account for 5% of all breast cancers in the United States and for 25% of breast cancers in women younger than age 30 years old.
Women of Ashkenazi (Eastern European) Jewish heritage have a slightly higher risk of breast cancer than does the general popula- tion (Box 2.2), but additional work is being done to determine whether this population has a higher rate of breast and ovarian cancer related to BRCA1 and BRCA2 mutations. Other genetic syndromes that have a higher risk of breast cancer include the Li-Fraumeni, Cowden, and ataxia-telangiectasia syndromes.
Factors such as early menarche (before age 12), late meno- pause (after age 55), nulliparity, and first live birth after age 30 bestow a slightly higher risk for breast cancer, as a result of hav- ing more menstrual cycles and longer exposure to estrogen and progesterone. Data from a 2003 study, part of the Women’s Health Initiative, which is a randomized, controlled trial of the effects of estrogen plus progestin (combination hormone replacement therapy [CHRT]) versus placebo, showed a 24% greater incidence of breast cancer in women receiving CHRT compared with the control group. Whereas previous data showed an adjusted rela- tive risk of 1.46 for the development of breast cancer in women receiving CHRT for more than 5 years, the 2003 analysis showed the risk for breast cancer rising within 5 years of starting CHRT;
in addition, it showed more difficulty in detecting cancers by mammography.
A breast biopsy showing atypical ductal hyperplasia (ADH) histology increases the risk for breast cancer to four to five times that of the general population. The presence of lobular carci- noma in situ (LCIS) also increases the risk for breast cancer, but at a much higher rate than ADH (about 10 times that of the normal population). The acronym LCIS is a misnomer and not a cancer at all; rather, LCIS is a high-risk marker for developing breast can- cer. A woman with LCIS has a 27% to 30% chance of developing
invasive ductal or lobular cancer in the ipsilateral or contralat- eral breast over a 10-year period. Thus a biopsy showing LCIS results in patient management of either “watchful waiting” with increased surveillance by frequent imaging and physical exami- nation, or bilateral mastectomy.
Women who had an early exposure to radiation also have an increased risk for breast cancer. A medical history of radiation therapy to the mediastinum for Hodgkin disease, multiple fluo- roscopic examinations for tuberculosis, ablation of the thymus, or treatment of acne with radiation infers scattered radiation to the breasts at an early age, which may induce breast can- cer. The risk for developing breast cancer is so high in women treated for Hodgkin disease that in 2007 the ACS recommended magnetic resonance breast cancer screening for Hodgkin dis- ease survivors as well as BRCA1/2 genetic mutation carriers or women with a high lifetime risk of breast cancer >20% to 25%
lifetime risk.
Extensive mammographic breast density, defined as a large amount of fibroglandular tissue within the breast by volume as measured on the mammogram, is associated with the risk of breast cancer. However, the association and the reasons for this finding, as well as its relative association among different ethnici- ties, are still being studied.
Other lifestyle choices also affect breast cancer risk. One of these is drinking alcohol. One drink per day bestows a very small risk, but two to five drinks per day increases the risk to 15 times that of women who do not drink. Being overweight or obese also increases the risk of cancer, especially if the weight gain happens after menopause and the fat is around the abdomen. A woman with an “apple-shaped” body is at higher risk than one with a “pear-shaped” body. Exercise has been shown to reduce breast cancer risk after menopause, with one study suggesting that cancer risk was reduced at least in part via hormonal path- ways. However, more study of these changeable risk factors is needed.
Despite all that is known about breast cancer risk factors, 70% of all women with breast cancer have none of these risk factors other than older age and female gender. What can women do to prevent breast cancer? The ACS recommends adopting a healthy lifestyle including exercise, maintenance of an appropriate body mass index, and decreased alcohol consumption. Women at very high risk also may take antiestrogen medications to prevent breast cancer.