However, a significant variation or sudden change in aspects, such as density, could indicate a problem. Discuss the results with your healthcare provider.
Learn more about breast asymmetry, its causes, how it relates to cancer, testing, and more.
Asymmetry on Mammogram Results
Asymmetry results on a mammogram indicate that the image shows something different on one breast than the other or to other parts of that same breast.
Types of breast asymmetry seen on a mammogram include:
Focal asymmetry: A difference in the breast seen on two or more mammogram images.
Developing asymmetry: Focal asymmetry that appears to grow or change compared to previous tests.
Global asymmetry: More breast tissue in one breast or one area of a breast.
When breast asymmetry is detected, additional testing may be recommended. However, this does not mean that breast asymmetry is cancerous.
Causes of Breast Asymmetry
Benign causes of breast asymmetry on mammogram include the following:
Fibrocystic changes: Cysts filled with fluid and scar tissue in the area of the cysts Dense stromal fibrosis: The connective tissue in that area of the breast is denser than it is in other areas Pseudoangiomatous stromal hyperplasia: A lump of non-cancerous cells that grows in the breast
Is Asymmetry a Sign of Cancer?
It is unclear how breast asymmetry impacts cancer risk, and it may depend on the cause of breast asymmetry. For example, fibrocystic changes do not increase cancer risk, nor does pseudoangiomatous stromal hyperplasia.
Stromal fibrosis can increase the risk of breast cancer and may be associated with inaccurate biopsies. This can happen when non-cancerous stromal fibrosis is located next to cancerous cells; a biopsy sample containing the non-cancerous stromal fibrosis is taken without catching any cancerous cells.
While breast asymmetry is not usually indicative of cancer, medical professionals may recommend testing to be sure.
Additional Screening Tests
When breast asymmetry is found on a mammogram, additional screening tests are usually recommended to rule out breast cancer. Further testing should not be a major reason for concern; many people with breasts who have a screening mammogram are asked to undergo additional testing, and less than 10% of them receive a breast cancer diagnosis. The type of further testing depends on what is found on the screening mammogram.
A diagnostic mammogram is similar to a screening mammogram but with additional images of the asymmetric area. 3D tomosynthesis, which uses X-ray technology like a mammogram, can take images from more angles, providing a more accurate result. Sometimes a combination of additional tests is recommended.
Outlook
Breast asymmetry is usually entirely normal and does not indicate an increased risk for cancer. However, it is important to see your healthcare provider for an evaluation and follow through with any recommended testing.
If the initial mammogram result of breast asymmetry does lead to a breast cancer diagnosis, it is a treatable condition with high survival rates.
Summary
Breast asymmetry means that breasts are of different sizes or shapes. When found on a mammogram, breast asymmetry means that there is a difference in one area of one breast in comparison to the rest of the breast, such as an area of breast tissue that is denser. While this can be a sign of cancer, it is normal to have some breast asymmetry; it is usually not cancer.
Even so, additional testing, such as a diagnostic mammogram or 3D tomosynthesis, may be recommended to ensure breast cancer is not overlooked.
A Word From Verywell
Breast asymmetry is entirely normal and not cancerous most of the time. If you or someone you know suspects or has been told they have breast asymmetry, help is available. Reach out to a healthcare provider, such as a gynecologist, oncologist, or primary healthcare provider. If breast asymmetry does lead to a breast cancer diagnosis, know that it is a treatable condition with high survival rates.
