Breast ultrasound is sometimes used to evaluate breast abnormalities that are found at screening or diagnostic mammography or on physical exam. Breast ultrasound is not routinely used for screening. Some studies have suggested that ultrasound be considered in screening of women with dense breast tissue (which is difficult to evaluate by routine mammography). But, use of ultrasound instead of mammography is not recommended because small calcium deposits, which are one of the earliest signs of cancer, are not visible by ultrasound. Ultrasound is useful for evaluation of some breast masses and is the only way to tell if a cyst is present without placing a needle into it to aspirate fluid. Cysts cannot be accurately diagnosed on physical exam alone. Breast ultrasound may also be used to help doctors precisely guide a biopsy needle into some breast lesions.

Imaging-guided Breast Biopsy

Mammography cannot prove that an area seen on the films is due to a cancer. If mammography raises a significant suspicion of cancer, a biopsy (a sample of cells or tissue removed for examination under the microscope by a pathologist) is needed to tell if the suspicious area is indeed cancer.

For years, excisional surgical biopsy was the only option for this purpose. The surgeon doing the biopsy makes an incision in the skin of the breast and removes the entire lesion (abnormal area) together with a narrow zone of normal tissue. Today many suspicious breast abnormalities can be diagnosed without surgery by using needle biopsy. There are two types of needle biopsies -- fine needle aspiration biopsy (FNAB) and core needle biopsy (CNB). FNAB uses a very thin needle to remove fluid and tiny fragments of tissue. CNB uses a slightly larger needle to remove a cylindrical piece of tissue about 1/16 inch in diameter and ½ inch long. If the breast mass is large enough to feel, the physician can directly guide placement of the biopsy needle by touch. But, even if an abnormality is too small to be felt, FNAB or CNB can still be done using breast imaging methods such as ultrasound and stereotactic mammography to guide the needle into the lesion.

During an ultrasound examination, the physician can view the needle on a screen as it moves toward and into the mass.

 OTHER METHODS

Mammography is an excellent way to find most breast cancers at their earliest and most curable stage. However, mammography does not detect all breast cancers. Tremendous research efforts are ongoing in the field of breast imaging in order to increase the number of cancers found at imaging before they are felt by the patient or her physician, to find cancers even smaller than those detected currently by mammography, and to improve the accuracy of breast imaging in distinguishing benign breast conditions from breast cancers. New methods being studied include magnetic resonance imaging (MRI), digital mammography, nuclear medicine studies, and computer aided diagnosis.

Magnetic resonance imaging (MRI) uses magnetization and radio waves, instead of x-rays, to produce very detailed, cross-sectional images. The most useful MRI examinations for breast imaging use a contrast material (Gadolinium DTPA) that is injected into a small vein in the arm before or during the examination. This contrast material improves the capability of MRI to clearly show details of breast tissue. It was hoped that MRI would be equal or better than mammography in diagnosing breast cancer. Although MRI can detect some abnormalities not seen on the mammogram, it is less accurate than routine mammography in determining which of the abnormal areas are cancer and which are not. Studies are underway to continue refining technology for breast MRI, and to better define the role of currently available instruments. Some radiologists have suggested that MRI might be useful in women whose routine mammograms show abnormal areas of uncertain significance. But, most radiologists feel that until the accuracy of MRI improves, it will remain an experimental technique that has limited use. As noted earlier, MRI is very useful in detecting rupture of breast implants. Just as x-ray mammography uses dedicated equipment (x-ray machines designed especially for mammography), breast MRI also requires special equipment. Higher quality images are produced by dedicated breast MRI equipment than by equipment designed for head, chest, or abdominal MRI scanning. However, most hospitals and imaging centers do not have dedicated breast MRI equipment available.