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Currently, mammography and breast exams by the doctor or nurse are the most common and useful techniques for finding breast cancer early. Other methods such as ultrasound may be helpful in narrowing the diagnosis for women who have suspicious breast changes. However, no other method is yet effective for screening women with no symptoms, and most of them are used primarily in research programs.
Ultrasound works by sending high-frequency sound waves into the breast. The pattern of echoes from these sound waves is converted into an image, called a sonogram, of the breast's interior. Ultrasound, which is painless and harmless, is especially good in distinguishing between tumors, which are solid, and cysts, which are filled with fluid. Sonograms of the breast can also be helpful in evaluating some lumps that can be felt but are hard to see on mammography, especially in the dense breasts of young women. Unlike mammography, ultrasound cannot detect the microcalcifications that sometimes indicate cancer, nor does it pick up small tumors.
Computed tomography, or CT scanning, uses a computer to organize the information from multiple x-ray views and constructs a cross-sectional image of the body. CT is sometimes helpful in locating breast lesions that are difficult to pinpoint with mammography or ultrasound-for instance, a tumor that is so close to the chest wall that it shows up in only one mammographic view.
Several even newer techniques for imaging the breast are in the research stage. These include Magnetic Resonance Imaging , or MRI, which relies on magnetic fields and radio waves to produce a likeness of body tissues, and Positron Emission Tomography (PET scanning) , which can identify tissues that are abnormally active. Laser beam scanning shines a powerful laser beam through the breast while a special camera on the far side of the breast records the image.
Research is also under way to develop laboratory tests that could be used to detect cancer in blood samples. Tumor markers are substances produced either by tumors or by the body in response to tumors. Elevated blood levels of certain biomarkers can be helpful in confirming a diagnosis or watching for tumor recurrence. However, because most biomarkers can be elevated even in some healthy people, they are not yet practical for screening for breast cancer.
Someday it may be possible to identify genetic changes that predispose women to breast cancer. At present, this type of testing is limited to certain rare families whose members are inclined to develop breast cancer at an early age and who have cells that carry an inherited genetic mutation.