The U.S. Preventive Services Task Force takes the stance that there is insufficient evidence to recommend for or against breast cancer screening with clinical breast examination alone (4). As stated earlier, the ACS guidelines do recommend regular clinical breast examinations. Given that 10% to 15% of breast cancers are mammographically occult, there is a role for clinical and breast self-examination as a complement to breast cancer screening as well as self-awareness. Women who detect breast tumors themselves typically find them outside of a structured examination, such as when bathing or getting dressed (4), so self-awareness is vital.

The historical evidence supporting the recommendation for screening mammography comes from eight randomized trials that were performed in Sweden, the United States, Canada, and the United Kingdom (4). Overall, breast cancers detected by screening mammography are smaller and have a more favorable history than those detected by clinical exam. A pooled analysis of the most recent data from all randomized trials of screening mammography in women aged 39 to 74 years showed a 24% reduction in mortality, although not all trials showed a statistically significant mortality reduction (4). Historically the United States has differed from Canada and other European countries in their recommendations for the interval of screening and the recommendations for the oldest and youngest women. In 2008 the National Health Service Breast Screening Program (NHSBP) in the United Kingdom issued an update on its 20-year anniversary. Although based on data showing that the best screening interval is likely 18 months to 2 years, based on cost-benefit study the U.K. program decided to offer screening every 3 years. In the United States women are encouraged to have a yearly mammogram starting at age 40 years, although given that 80% of breast cancers occur in women over 50 years, there is a minimal survival benefit to screening women under the age of 50 years. Screening the 40- to 49 year age group leads to 0.8 death avoided per 1,000. The NHSBSP encourages these younger women to understand the limitations of screening this age population and notes that private facilities do offer the service (5). The Canadian health service similarly reviewed their results, and their final recommendation was that women in the 40- to 49-year age group should be told the risks and benefits and allowed to decide for themselves when they wish to start screening (6). A review from the Cleveland Clinic stated that, based on meta-analysis, screening women in their 40s decreases breast cancer death rates by about 20% (7). The guidelines in the United States indicate to start screening at age 40 years in the average-risk woman.

Life expectancy continues to increase, and in developed countries women aged 75 years and older represent an increasing percentage of the population (8). Evidence-based guidelines for the regular screening of older women are lacking. Based on review of the literature, the authors found a consistent higher risk of death from breast cancer among nonusers compared to regular users of screening mammograms in the 75- to 84-year age group. This was also seen in the >85 years age group, although it was not statistically significant. Patients
with life expectancies less than 5 years are not likely to derive any survival benefit from cancer screening (8). Age in itself should not be a reason to stop screening but rather the patients overall health and ability to receive treatment and benefit from the screening.

Ultrasound uses high-frequency sound waves to create a picture of an area of interest. As there is no ionizing radiation, it is useful in young and pregnant women. Ultrasound is able to look at only a small area of the breast at a time and it is very operator and patient dependent (4). Ultrasound is generally not used as a screening device but can be used to evaluate palpable masses or mammographic and MRI-detected lesions. Ultrasound may increase the sensitivity of screening if it is used as an adjunct to mammography for women shown to have radiologically dense breasts, but it is likely to increase the number of women requiring biopsy for benign findings (14). In general it is not a useful screening tool. In a single-institution review of new breast malignancies identified solely by ultrasound, a total of 34,694 breast sonograms were performed at an outpatient radiology affiliate between April 1998 and April 2006. Of all cancers diagnosed, 2.2% were identified solely by sonography. The number of cancers identified relative to the total number of sonograms done was 0.03% (15). Given these numbers, ultrasound should be used selectively. Ultrasound is 96% to 100% sensitive in detecting breast cysts. Ultrasound is less effective in demonstrating solid masses. Bassett et al. found that only 63% of solid masses were visible on ultrasound (16). Breast ultrasound does not consistently detect microcalcifications (17). If a palpable mass or asymmetry is not clinically suspicious, and the mammogram and ultrasound are both negative, the risk for cancer is low, but the possibility of cancer still exists. Diagnostic options then include either a biopsy or close observation. Ultrasound is a great adjunct to breast biopsy. It can guide fine needle aspiration (FNA), core biopsy, or placement of a localizing wire for an excisional biopsy more easily for both the patient and breast imager than can other imaging modalities.

MRI produces images from a combination of a strong magnetic field, radio waves, and computer processing. Every study on MRI has reported higher sensitivity than mammography, ultrasound, or both. Specificity of MRI tends to be lower than that of mammography (17). In a study of 1,909 women in the Netherlands the authors noted that screening MRI led to twice as many unneeded additional examinations and three times as many unneeded biopsies as did screening with mammography (18). Current research is focused on the suitability of MRI as a screening modality in conjunction with mammography in high-risk populations. The limitations of MRI include its high cost, unsuitability for some patients (those who are obese, have pacemakers, or have renal failure), the potential for unnecessary biopsies, lack of portability and the length of time required for imaging. The patient receives an intravenous line and is given gadolinium for contrast enhancement. Then 20 minutes of motionless scan time follows (4). There are three different patterns of dynamic enhancement. The type 1 pattern (persistent) shows slow, progressive contrast uptake over time and is suggestive of benignity. The type II contrast pattern (plateau)
shows a rapid uptake in contrast and then a leveling off of uptake. This pattern is suggestive of malignancy. The type III pattern (washout) is indicative of malignancy (10). The diagnostic evaluation must also include the assessment of lesion morphology, which requires high-resolution imaging. The border of the lesion is the most important feature. Spiculated and irregular margins have a positive predictive value of malignancy ranging from 76% to 91%. Most benign masses have a smooth border with a negative predictive value for malignancy of 90% (10,19). DCIS is suggested by small, clumped foci that are within a segment or duct (20).