Breast Cancer Imaging
Mammography, Ultrasonography, and Magnetic Resonance Imaging
The evaluation of breast cancer includes at least one imaging study. What are the modalities for imaging breast cancer and when are they used?
Breast cancer is one of the most common conditions among women in the United States. The importance of screening cannot be stressed enough. Through clinical evaluation, imaging studies, and biopsies as needed, the chances of detecting breast cancer early are greater. Many topics related to breast cancer deserve consideration. Among them are the methods of breast cancer imaging.
Mammography
A mammogram is essentially an x-ray of the breast, used for screening breast cancer in asymptomatic women and diagnosing breast cancer in women who have symptoms. During the test, the breast is compressed in order to minimize x-ray scatter and maximize image quality. This may be uncomfortable but not necessarily painful. From there, x-ray images are shot at different angles.
The radiologist reviews the images to look for abnormalities like masses, densities, and structural irregularities. Calcifications, or soft tissue hardening with calcium deposits, are especially important. They are often an early sign of breast cancer, especially if the calcifications are small (microcalcifications) or irregularly shaped. Calcifications appear bright on x-ray imaging, one reason why mammograms are the standard tool for breast cancer screening.
The study does have some limitations. Imaging is more difficult with breasts that are dense or breasts in younger women. Breasts with implants or significant surgical scars are also difficult to visualize on mammography. Nevertheless, mammography is recommended for breast cancer screening starting at age 40 and for diagnosing suspected breast cancer as indicated.
Ultrasonography
An ultrasound of the breast is currently used as a diagnostic tool. If a physician notes a lump or other suspicious finding on a clinical breast exam, he or she may evaluate further with an ultrasound. This can tell if the abnormality is a hollow cyst or something solid and if it has malignant characteristics like irregular shape and calcifications. Ultrasound is also used as an imaging guide during a needle biopsy of a suspicious breast mass.
Ultrasound as a means of screening breast cancer is under investigation. Challenges exist that hinder the acceptance of ultrasound screening. The technique may require proficient skill and optimal imaging. There is also a risk of missing microcalcifications that can show up on mammography but not on ultrasound. Until studies demonstrate equivalent or greater efficacy than mammography, ultrasound is not recommended as a breast cancer screening tool.
Magnetic Resonance Imaging
MRI of the breast has been explored and improved over the years. It has the advantages of flexible angles of visualization and not using ionizing radiation. However, it is an expensive modality with questionable screening capabilities. It can still help diagnose breast cancer, but usually in conjunction with mammography and not alone. Like breast ultrasound, MRI for screening breast cancer is being researched in ongoing studies.
Final Words
Mammography continues to be the standard screening tool for breast cancer, but that does not mean it will forever be this way. If future research demonstrates superior imaging methods of screening and diagnosing breast cancer, women can expect a dramatic change in their preventive care.
References
- eMedicine - Breast Cancer Mammography
- eMedicine - Breast Cancer Ultrasonography
- eMedicine - Magnetic Resonance Mammography
