Being called back for a diagnostic mammogram after a routine screening can understandably cause apprehension. A diagnostic exam is simply a focused follow-up to obtain clearer information about an area of concern identified during the initial screening. This specialized examination is structured to move quickly from image acquisition to interpretation, often providing answers before the patient leaves the facility.
Defining the Diagnostic Approach
The diagnostic mammogram is a targeted investigation, unlike a screening mammogram. While a screening exam is routinely performed on asymptomatic women, the diagnostic exam is ordered when a specific concern exists, such as a palpable lump, unexplained nipple discharge, or an area that appeared unclear on a prior screening image. Unlike a screening, which typically involves only two standard views of each breast, the diagnostic approach allows for specialized views tailored to the specific finding. A breast imaging radiologist is often present or immediately available to review the images as they are acquired. The goal is to fully characterize the area of interest—whether it is a mass, a cluster of microcalcifications, or architectural distortion—to determine if it is benign or requires further action.
The Procedure Detailed Imaging Acquisition
The diagnostic procedure begins similarly to the screening, with the technologist positioning the breast in the mammography unit. However, the subsequent images are specific views directed by the radiologist to hone in on the area in question. The technologist often starts by taking a standard view to confirm the location before proceeding to specialized techniques. One common technique is spot compression, which uses a smaller compression paddle to apply focused pressure directly onto the suspicious tissue. This localized compression helps to spread out overlapping tissue, allowing a clearer look at the borders of a mass or density.
Another specialized technique is the magnification view, which uses a platform to position the breast away from the detector, effectively creating a zoomed-in image. Magnification views are useful for evaluating the morphology and distribution of tiny calcium deposits, known as microcalcifications, which can sometimes be an early sign of cancer. The technologist is meticulous in centering the area of concern, often requiring multiple adjustments to ensure the best possible image quality. Because the radiologist is guiding the process, the patient may be asked to wait while preliminary images are checked, ensuring all necessary information is gathered.
Interpretation and Post-Procedure Follow-Up
The defining feature of a diagnostic mammogram is the immediate, real-time involvement of the radiologist, who interprets the images while the patient waits. This immediate review allows the radiologist to determine if the additional views have resolved the finding, revealed a benign structure, or confirmed a persistent abnormality. The comprehensive assessment of all images, including the original screening film and the new diagnostic views, allows for an accurate classification of the finding. The results are standardized using the Breast Imaging Reporting and Data System (BI-RADS), a scoring system that assigns a number from 0 to 6 to communicate the finding and recommend the next course of action.
A BI-RADS score of 1 or 2 indicates a negative or benign finding, respectively, meaning the patient can return to routine annual screening. A score of 3 means the finding is probably benign, with a very low likelihood of being cancerous (less than 2%), and typically leads to a recommendation for a short-term follow-up mammogram in six months to monitor for stability. Scores of 4 (suspicious abnormality) or 5 (highly suggestive of malignancy) indicate a need for further tissue sampling, usually through a biopsy, to establish a definitive diagnosis. In many facilities, the radiologist or a nurse navigator will communicate these results and the recommended next steps to the patient on the same day as the diagnostic examination.