Receiving an “abnormal” mammogram result often causes anxiety, but this finding does not mean cancer is present. Statistically, only about 10% of women undergoing routine screening are called back for additional testing following an initial abnormal finding. The vast majority of this group will ultimately be found to have a benign, or non-cancerous, condition. In fact, fewer than 5% of all women recalled for further evaluation are ultimately diagnosed with breast cancer.
Understanding Abnormal Mammogram Results
A radiologist identifies a screening mammogram as abnormal when it shows a deviation from a negative or clearly benign finding. These deviations typically fall into three categories: a mass or lump, suspicious calcifications, or an architectural distortion in the breast tissue. The initial screening is highly sensitive, prioritizing the early detection of possible cancer.
Radiologists use the standardized Breast Imaging Reporting and Data System (BI-RADS) to communicate findings and recommend next steps. This six-category scale provides a consistent framework for interpreting results across different facilities. An abnormal result often corresponds to a BI-RADS Category 0 or Category 3.
A BI-RADS Category 0 is assigned when the image is considered “Incomplete,” meaning the radiologist needs additional imaging or older mammograms for comparison. A Category 3 result indicates a “Probably Benign Finding,” meaning the likelihood of malignancy is less than 2%. Short-term follow-up is recommended for Category 3 to confirm stability over time. These two categories are the most common reasons for a recall and are usually resolved without a cancer diagnosis.
Common Non-Cancerous Causes
Several common, benign conditions frequently mimic cancer on initial mammography, leading to the call for further testing. One of the most prevalent causes is fibrocystic change, a condition where the breast tissue develops a lumpy, rope-like texture due to fibrosis and fluid-filled cysts. These changes are often hormone-related, with symptoms of tenderness and swelling frequently worsening before the menstrual cycle.
Another frequent finding is the presence of calcifications, which are tiny calcium deposits within the breast tissue that appear as small white spots on the image. These are classified by size into macrocalcifications and microcalcifications. Macrocalcifications are larger, coarse deposits that are almost always benign and typically require no follow-up.
Microcalcifications, which are very fine specks, require closer scrutiny because certain patterns—like those that are tightly clustered or irregular in shape—can sometimes be associated with early cancer. However, many patterns of microcalcifications are also benign, stemming from causes such as old injuries, inflammation, or cell secretions. Simple cysts, which are smooth, fluid-filled sacs, and fibroadenomas, which are solid, non-cancerous tumors common in younger women, are also frequent benign causes of abnormal masses on a mammogram.
Navigating the Follow-Up Procedures
The process that follows an abnormal screening mammogram is a structured sequence designed to definitively characterize the initial finding. The first step typically involves a diagnostic mammogram, which focuses on the area of concern with specialized compression and magnified views. This focused imaging often resolves the finding by showing that the initial abnormality was simply overlapping glandular breast tissue.
If the finding persists, a breast ultrasound is often performed. Ultrasound uses sound waves to quickly determine if a mass is a fluid-filled cyst or a solid lump. An ultrasound can also guide the physician to the exact location of the abnormality for a biopsy if needed.
If the imaging workup remains suspicious, particularly for a BI-RADS Category 4 or 5 result, a tissue biopsy is the next logical step, as it is the only way to obtain a conclusive diagnosis. The most common method is a core needle biopsy, which uses a hollow needle to remove small cylinders of tissue for pathological examination.
For non-palpable abnormalities like microcalcifications, a stereotactic or vacuum-assisted biopsy may be used. This employs mammography or ultrasound guidance to precisely target the area. Even when a biopsy is necessary, most confirm a benign condition, providing a final answer and allowing the patient to return to routine screening.