Mammography is a widely used imaging technique for the early detection of breast changes. It uses low-dose X-rays to create detailed images of internal breast tissue. Its primary purpose is to screen for breast cancer and other breast conditions, often identifying potential concerns before they can be felt. Mammograms help healthcare providers monitor breast health over time, aiding in timely diagnosis and treatment.
Understanding Summation Artifacts
A summation artifact on a mammogram is an optical illusion occurring when normal breast tissues overlap, mimicking an abnormality. This happens because a mammogram compresses the three-dimensional breast into a two-dimensional image. As X-rays pass through different layers of normal breast tissue, these structures can superimpose on one another, resulting in an area of increased density that looks like a potential lesion or mass.
The breast is composed of various tissues, including glandular tissue, fibrous connective tissue, and fat. When these normal components are compressed and projected onto a flat image, their combined densities can create a false impression of a suspicious finding. Breast density can contribute to the likelihood of summation artifacts, as denser breasts contain more glandular and fibrous tissue, leading to more potential for overlap. More than 75% of asymmetries seen on mammograms are summation artifacts. These artifacts are essentially “pseudo-masses” that do not represent a true lump or cancerous growth.
Appearance of Summation Artifacts
Summation artifacts can present on a mammogram in various ways, often appearing as a focal asymmetry, which is an area of increased tissue density seen in one or sometimes two projections that does not have the clear-cut borders of a mass. They might look like a fuzzy area, an irregular shape, or a mass-like density on the image. These findings can resemble actual abnormalities, leading to further investigation.
This visual ambiguity is why radiologists often need to perform additional imaging to clarify the nature of these findings. The perceived abnormality from a summation artifact will typically be visible on only one of the standard mammogram views and will not be seen on additional views taken from different angles.
Distinguishing From Actual Findings
Radiologists employ several specialized techniques to differentiate a summation artifact from a true lesion. Initial mammograms typically involve two standard views of each breast. If a focal asymmetry is identified on only one of these views, it often raises the suspicion of a summation artifact. In such cases, additional mammographic views are obtained to “unroll” or spread out the breast tissue.
These additional views include spot compression views, which apply localized pressure to the area of concern, and magnification views, which provide a more detailed look at the tissue. A rolled view, where the breast tissue is gently repositioned, can also help determine if the apparent abnormality persists. If the suspicious area disappears or resolves on these additional views, it confirms that it was a summation artifact caused by overlapping normal tissue.
Three-dimensional mammography, also known as digital breast tomosynthesis (DBT), is another powerful tool used for this differentiation. DBT acquires multiple low-dose X-ray images from different angles, which are then reconstructed into a series of thin slices, effectively creating a 3D image of the breast. This slicing technique helps radiologists see through overlapping tissues, making it easier to determine if a perceived abnormality is a true lesion or merely a summation artifact. Tomosynthesis has been shown to reduce the number of benign recalls, improving the specificity of mammography.
Navigating Next Steps
If a summation artifact is suspected on a mammogram, patients are often called back for additional imaging. This callback is a routine part of breast imaging and does not automatically mean that cancer is present. In fact, the majority of callbacks for additional imaging, approximately 9 out of 10, ultimately turn out to be benign findings, including summation artifacts. The purpose of these follow-up tests is to clarify the initial findings and ensure accurate diagnosis.
During a callback, a patient may undergo diagnostic mammograms, which are more focused images of the specific area of concern, or breast ultrasound. An ultrasound uses sound waves to create images and can help distinguish between solid masses and fluid-filled cysts, further aiding in the clarification of a finding. Open communication with healthcare providers is important throughout this process, as they can explain the specific reasons for the callback and the planned next steps.