Mammography is a powerful screening tool designed to detect breast cancer early, often before any physical symptoms appear. While the vast majority of women receive a normal result, receiving a notification for a “callback” or an abnormal finding can cause significant anxiety. It is important to understand that an abnormal result is not a diagnosis of cancer; rather, it is a signal for the medical team to gather more information. This article provides context and definitive statistics to clarify what an abnormal mammogram means and what the next steps entail.
Defining an Abnormal Mammogram Result
An abnormal result indicates that the initial images contained an area that the radiologist could not definitively classify as normal or benign. To standardize communication among healthcare providers, radiologists use the Breast Imaging Reporting and Data System (BI-RADS), which assigns a score from 0 to 6. An abnormal finding that requires further investigation is classified as BI-RADS Category 0, meaning the assessment is incomplete.
This classification means that additional imaging is required to reach a final conclusion. The suspicious findings that prompt this need for more information often fall into three main categories: masses, which are three-dimensional lesions that may be solid or fluid-filled; microcalcifications, which are tiny specks of calcium deposit in the breast tissue; and architectural distortion, where the breast tissue structure appears pulled or distorted without a clear mass being visible.
The True Statistics: Rates of Abnormal Results
Across all screening programs, the percentage of women who are asked to return for additional testing typically falls between 7% and 10%. This callback rate represents the need for a clearer picture, not a cancer diagnosis. For every 1,000 women who undergo a screening mammogram, approximately 70 to 100 will be called back for a closer look.
The overwhelming majority of these callbacks do not lead to a cancer diagnosis. Of all women screened, only about 0.5% will ultimately be diagnosed with breast cancer. This means that for the women called back, less than 10% will be found to have a malignancy.
The term “false positive” refers to an abnormal result that, upon further testing, turns out to be benign. These false-positive findings, such as non-cancerous cysts or benign calcifications, account for the vast number of callbacks. Even among the small fraction of women recommended for a biopsy, 60% to 70% of those procedures will confirm that no cancer is present. This low cancer yield confirms that the screening process is highly sensitive.
What Happens After an Abnormal Result?
The first step after a callback is a diagnostic workup, which provides the radiologist with more detailed images to complete the assessment. This typically begins with a diagnostic mammogram, which uses special views like magnification and spot compression to focus on the area of concern. Unlike the initial screening, the radiologist is often present to guide the technologist and tailor the images based on the specific finding.
Following the tailored mammogram, a breast ultrasound is often performed, particularly if a mass was detected. Ultrasound uses sound waves to create an image and is highly effective at determining if a mass is a fluid-filled cyst, which is nearly always benign, or a solid mass that requires further scrutiny. The combination of diagnostic mammography and ultrasound clarifies the nature of most initial abnormal findings.
If the additional imaging cannot definitively classify the finding as benign, the next step is a biopsy to obtain a tissue sample for laboratory analysis. A biopsy is the only way to confirm a cancer diagnosis and is typically a minimally invasive procedure, such as a core needle biopsy, performed using imaging guidance.
Factors Influencing Abnormality Rates
Several factors influence the likelihood of an individual receiving a callback, causing rates to fluctuate significantly from the population average. One of the most prominent factors is whether the screening is a woman’s first mammogram. Without prior images for comparison, the radiologist lacks a baseline, and a finding that may be normal often triggers a callback.
Breast density is another major variable, as dense breast tissue appears white on a mammogram, which can obscure potential masses or lesions. This “masking” effect decreases the accuracy of the mammogram and often leads to higher callback rates for women with dense breasts. Density is influenced by age and hormone status, with younger, premenopausal women generally having denser breasts than older women.
While screening accuracy generally increases with age, younger patients tend to have higher callback rates primarily due to their higher breast density. Understanding these individual factors helps explain why a personal callback risk may be higher or lower than the overall population statistics.