Receiving a notification that your screening mammogram result is “abnormal” or “incomplete” often causes intense worry. The need for further testing frequently leads to concern that a serious illness has been detected. This initial finding is a very common occurrence in breast screening programs. The vast majority of women called back for additional imaging do not have a cancer diagnosis. This follow-up process is a standard part of breast health care designed to provide the clearest possible picture of your tissue.
What “Abnormal” Really Means and How Common It Is
An abnormal mammogram means the radiologist detected a finding requiring a closer look, such as a mass, calcification, or tissue distortion. Approximately 10% of women who undergo a screening mammogram are called back for additional testing. This high recall rate is part of comprehensive screening, which errs on the side of caution for early detection. For every ten women recalled, only one or two will ultimately be diagnosed with cancer, meaning up to 95% of abnormal findings are not cancerous.
To standardize communication, radiologists use the Breast Imaging Reporting and Data System (BI-RADS). An abnormal result often falls into one of two categories. A BI-RADS Category 0 means the image is “Incomplete” and requires further evaluation, such as a diagnostic study or comparison with previous mammograms. This classification is frequently used when dense breast tissue obscures the image or when tissue overlap mimics a mass.
A BI-RADS Category 3 finding is labeled “Probably Benign,” indicating the radiologist is highly confident the finding is harmless, with a greater than 98% chance of being non-cancerous. The recommended action is typically a short-interval follow-up mammogram, usually in six months, to confirm the finding’s stability over time.
The Diagnostic Process: Understanding Your Next Steps
The first step after an abnormal screening result is usually a diagnostic mammogram, a specialized examination focusing on the area of concern. Unlike routine screening, which takes two standard views of each breast, the diagnostic exam employs additional, highly targeted views. These views may include magnification or spot compression, which flatten a smaller area of tissue to clarify the finding. A radiologist is often present during this procedure to review the images in real time and determine the next course of action.
If the diagnostic mammogram does not resolve the finding, a breast ultrasound is typically performed during the same visit. This technique uses high-frequency sound waves to create a real-time image of the tissue. Ultrasound is effective at determining if a detected mass is a solid lump or a simple, fluid-filled sac, known as a cyst. A simple cyst is a benign finding and often requires no further action.
If the mass is solid, or if calcifications have a suspicious pattern, the next step may be a biopsy to obtain a definitive diagnosis. The most common type is a core needle biopsy (CNB), a minimally invasive procedure performed with local anesthesia. Under guidance from ultrasound or stereotactic mammography, a hollow needle removes small, cylinder-shaped tissue samples for laboratory analysis. This provides the pathologist with enough tissue to determine the cellular composition of the abnormality.
A surgical biopsy, also called an open biopsy, is less common. It involves the surgeon removing all or part of the suspicious area in a hospital setting. This procedure is typically reserved for cases where needle biopsy results are inconclusive or if the area is difficult to access. The overarching purpose of these diagnostic steps is to move from an uncertain image to a clear, conclusive diagnosis with the least invasive means possible.
Common Non-Malignant Reasons for Follow-Up
Many factors unrelated to cancer can cause an abnormal appearance on a mammogram, leading to follow-up. Breast cysts are frequent causes, presenting as benign, fluid-filled sacs. These are often related to hormonal changes and are identifiable as harmless using ultrasound.
Another common finding is breast calcifications, which are tiny calcium deposits within the tissue. While some patterns of microcalcifications can be concerning, the vast majority are macrocalcifications, which are coarser, larger deposits that are almost always benign, occurring with aging or past inflammation. A closer diagnostic view is needed to differentiate between the two types.
Dense breast tissue is a structural feature, not a disease, where there is more glandular and fibrous tissue than fatty tissue. This density appears white on a mammogram, potentially obscuring a true abnormality or mimicking a mass due to tissue overlap. Fibroadenomas are also a frequent cause for recall; these are firm, benign solid tumors often found in younger women. Finally, scar tissue from prior procedures or old injuries can alter the tissue architecture, creating a distortion that appears suspicious.