When a routine screening mammogram leads to a request for additional imaging, the initial reaction is often concern. This experience is common, with roughly 10% of women receiving a callback after their initial screening. This request does not typically mean cancer has been found, but rather that the radiologist requires a clearer, more focused look at a specific area. The initial screening mammogram takes a broad survey of the breast tissue, while the second appointment, known as a diagnostic mammogram, is a targeted investigation.
Why Screening Mammograms Require a Second Look
A primary reason for a callback is the inherent difficulty of capturing a three-dimensional breast structure in a two-dimensional X-ray image. When the breast is compressed, normal tissue can overlap, creating a dense shadow known as a “summation artifact” or focal asymmetry. This shadow can mimic a solid mass, prompting the need for a targeted view to confirm that the appearance is simply overlapping tissue.
Another frequent cause is the presence of dense breast tissue, which appears white on a mammogram, similar to cancerous masses. If a woman has dense breasts, the radiologist’s ability to see through the tissue is reduced. Additional imaging is required to penetrate the dense tissue and ensure no small masses are hidden or mimicked by the density itself.
Sometimes, the initial image may be technically suboptimal due to patient movement or positioning, preventing the radiologist from seeing all the tissue clearly. A comparison to previous mammograms may also show a subtle change, such as a new cluster of tiny calcium deposits known as calcifications. Although the majority of these changes are benign, they still require a closer examination to confirm their nature.
The Difference in Diagnostic Procedures
The follow-up appointment is called a diagnostic mammogram because its purpose is to diagnose or rule out a specific finding, unlike the general screening exam. This appointment typically takes longer, and a radiologist is often present to guide the technologist and review the images immediately. The procedure involves specialized techniques designed to resolve the ambiguity seen on the initial screening.
One common technique is spot compression, which uses a smaller paddle to apply pressure only to the area of concern. This focused compression separates the overlapping tissue and flattens the specific region. This helps the radiologist determine if the shadow is a real mass or merely a summation of normal structures. Another technique is magnification views, which zoom in on tiny details, such as the shape and borders of calcifications, to assess their probability of being benign.
Frequently, the diagnostic workup includes an ultrasound of the area in question, which uses sound waves instead of radiation. The ultrasound is effective for distinguishing between a solid mass and a fluid-filled cyst, as cysts are almost always benign and do not require further intervention. Combining the targeted mammogram views with an ultrasound provides a comprehensive assessment of the area of concern.
Understanding the Final Results and Next Steps
The results of the diagnostic mammogram are reported using the Breast Imaging Reporting and Data System (BI-RADS), a standardized scoring method. The initial inconclusive screening result is categorized as BI-RADS 0, meaning more information is needed to make a final assessment. The diagnostic procedure is performed to assign a definitive category.
If the diagnostic imaging resolves the concern, the result will be categorized as BI-RADS 1 (negative) or BI-RADS 2 (benign finding). This confirms the tissue is normal or that the finding is non-cancerous, such as a simple cyst. In these cases, the patient returns to their regular annual screening schedule. A finding categorized as BI-RADS 3 means the abnormality is probably benign, having a chance of malignancy of 2% or less.
A BI-RADS 3 result usually leads to a short-interval follow-up, such as a repeat mammogram in six months, to ensure the finding remains stable. If the diagnostic images show a suspicious finding, the result will be categorized as BI-RADS 4 or 5, indicating a need for a biopsy. Even if a biopsy is required, the majority of lesions sent for testing are ultimately found to be benign.