Getting a call back after a screening mammogram can cause immediate anxiety, but an “abnormal” finding is a common occurrence. A screening mammogram is a general X-ray intended to find anything that looks different from normal tissue, and it is not a diagnostic tool. The purpose is to cast a wide net, and it is standard for a small percentage of women to be called back for a closer look. For women undergoing a routine screening, the callback rate is typically between 5% and 12%, and over 90% of those called back are ultimately found to be cancer-free. This initial result simply means the radiologist needs additional information to make a final assessment.
Understanding the BI-RADS Classification System
Radiologists use a standardized scoring system called the Breast Imaging Reporting and Data System, or BI-RADS, to categorize mammogram results consistently. This system translates complex imaging findings into a single number from 0 to 6, indicating the degree of suspicion and the recommended next steps. A score of 0, for instance, often triggers a callback, meaning the initial image was “Incomplete” and requires further evaluation. The radiologist may have seen a potential abnormality but needs more views or comparison with prior images to accurately categorize it.
The BI-RADS categories provide a clear roadmap for patient management. A score of 1 means the result is negative with no significant findings, while a score of 2 indicates a benign (non-cancerous) finding was noted, such as a simple cyst, but no further action is needed. When the finding is “Probably Benign,” the result is assigned a BI-RADS 3, meaning the chance of malignancy is less than 2%. In these cases, a short-interval follow-up, typically in six months, is recommended instead of an immediate biopsy, to confirm the finding remains stable over time.
A BI-RADS 4 suggests a “Suspicious Abnormality” that warrants a biopsy, with the chance of cancer ranging from 2% to 95%, depending on the specific characteristics of the finding. This category is sometimes broken down into three subcategories to reflect low, moderate, and high suspicion. The highest initial category is BI-RADS 5, which means the finding is “Highly Suggestive of Malignancy,” with a probability of cancer exceeding 95%. A BI-RADS 6 is only assigned after a biopsy confirms a cancer diagnosis.
Non-Cancerous Reasons for Abnormal Findings
Most abnormal screening results are due to benign conditions that can mimic suspicious masses or calcifications on a two-dimensional X-ray image. One frequent reason for a callback is dense breast tissue, which appears white on a mammogram, making it difficult to distinguish from potential masses that are also white. Approximately 40-50% of women have dense breast tissue, and this glandular and fibrous tissue can effectively obscure a small lesion.
Another common finding is calcifications, tiny specks of calcium that show up as bright white spots. Macrocalcifications are large, coarse deposits usually scattered randomly and are nearly always benign, often relating to aging arteries or old injuries. Microcalcifications are much smaller and can be a sign of early cancer if they appear in a tight cluster or linear pattern, though they are often benign and related to conditions like fibroadenomas or previous infections.
Solid, movable lumps called fibroadenomas are the most frequent benign breast mass, especially in younger women. These masses are composed of normal breast cells and appear well-defined and rounded on a mammogram. Cysts are also common, representing fluid-filled sacs seen on imaging. Unlike solid tumors, cysts are rarely associated with cancer.
The Necessary Diagnostic Follow-Up Procedures
When an initial screening mammogram is abnormal, the next step is typically a diagnostic mammogram, a more focused and detailed procedure. This exam involves taking additional, often magnified, X-ray views of the specific area of concern. The radiologist is present to guide the technologist and determine if the abnormality is confirmed or resolves with different positioning.
If the finding persists, the next procedure is often a breast ultrasound, which uses sound waves instead of radiation. Ultrasound is highly effective because it can immediately determine if a mass is solid or fluid-filled. A mass that transmits sound waves is nearly always a simple cyst, whereas a solid lump requires further investigation. For women with dense breasts, ultrasound can also help detect small tumors hidden on the mammogram.
If the additional imaging confirms a suspicious solid mass or concerning microcalcifications, a breast biopsy is recommended for a definitive diagnosis. The biopsy is the only way to confirm if cells are cancerous, and most biopsies ultimately show benign results. Common methods include core needle biopsies, which use a hollow needle to extract tissue, often guided by ultrasound or stereotactic mammography. Fine-needle aspiration samples cells or fluid, often for evaluating a cyst, while a surgical biopsy involves removing part or all of the lesion.