Difference Between Diagnostic and Screening Mammography
A screening mammogram consists of 2 standard x-ray images of each breast used to detect cancer in asymptomatic women, while a diagnostic mammogram includes additional specialized views (spot compression, magnification) to investigate a specific finding, whether from an abnormal screening result or a clinical symptom like a palpable mass. 1
Purpose and Clinical Context
Screening Mammography
- Used exclusively for asymptomatic women to detect unsuspected cancer that has the potential to be cured 2
- Performed as routine surveillance at regular intervals (typically annually) 1
- Consists of 2 standard radiographic views of each breast 1
- Results in BI-RADS categories 1-2 (negative/benign) lead to routine screening in 1 year 1
Diagnostic Mammography
- Used in two distinct situations: (1) evaluating a clinical finding such as a palpable mass, breast pain, or nipple discharge, and (2) additional imaging after an abnormal screening mammogram (recall/callback) 1
- Includes specialized views such as spot compression to evaluate nodule margins or magnification views to characterize microcalcifications 2, 3
- Often combined with ultrasound, particularly for masses or asymmetries 1
Technical and Performance Differences
Imaging Characteristics
- Diagnostic mammography has higher sensitivity but lower specificity compared to screening mammography 1
- Digital breast tomosynthesis may replace traditional diagnostic mammographic imaging in certain situations 1
- Diagnostic evaluation may include multiple imaging modalities (mammography, ultrasound, sometimes MRI) to render a final combined assessment 1
Assessment and Follow-up
- Screening mammograms use BI-RADS category 0 ("needs additional imaging evaluation") when findings require diagnostic workup 1
- Diagnostic mammography aims to provide a definitive assessment (BI-RADS 1-6) after complete evaluation 1
- The same BI-RADS terminology is used for both screened (asymptomatic recalled) women and symptomatic women, which can create confusion 1
Critical Clinical Pitfalls
Common Ordering Errors
- A palpable breast mass should always receive a diagnostic mammogram, not a screening mammogram 4
- Studies show 8.7% of patients with self-reported breast symptoms incorrectly had screening mammograms ordered rather than diagnostic 4
- This error can lead to increased cost and delay in diagnosis 4
Interpretation Limitations
- A negative mammogram (screening or diagnostic) does not rule out cancer in the presence of a palpable mass 5, 3
- Approximately 1 in 10 women with a breast lump or abnormal mammography will have breast cancer 3
- Diagnostic mammography should not affect the decision to biopsy a clinically suspicious palpable mass 3
Importance of Prior Images
- Radiologists should always attempt to obtain previous mammograms when evaluating abnormal findings, particularly for lesions of low suspicion 1, 6
- Comparison with prior images helps determine if a questionable area is benign, potentially avoiding unnecessary diagnostic procedures 6
- For BI-RADS category 0 findings, comparison with previous mammograms is a key component of proper evaluation 6
- Patients should bring images and reports from previous mammograms to their appointment 7