False-negative breast screening assessment: what lessons can we learn?

To review women who have had breast cancer diagnosed following previous assessment of a screen-detected mammographic abnormality in order to ascertain the frequency and characteristics of false-negative assessment.

The assessment process was reviewed in the study population of 28 women. This included the nature of the lesion recalled for assessment, additional mammography, clinical and ultrasound findings, and the results of fine needle aspiration cytology and needle histology.

The frequency of false-negative assessment was approximately 0.56%. The median time between false-negative assessment and diagnosis of breast cancer was 33 months. The most common mammographic lesion resulting in false-negative assessment was micro-calcification seen in 12 cases (43%). Only five of these 12 cases had image-guided biopsy, the remainder were thought to be benign on magnification views. Other mammographic abnormalities were nine masses (32%), five architectural distortions (18%) and two asymmetric densities (7%). Of the 16 women with mammographic lesions other than micro-calcifications 10 had a normal ultrasound.

Radiological interpretation of indeterminate micro-calcifications as benign or malignant is unreliable. An isolated cluster of micro-calcification requires image-guided core biopsy with representative micro-calcification obtained on specimen radiography. Further mammography done at assessment, particularly paddle compression views, should be carefully analysed to ensure areas of architectural distortion have truly resolved. If one imaging modality shows a significant abnormality and another does not the cases must be managed on the basis of the abnormal finding. Burrell, H.C.et al. (2001). Clinical Radiology56, 385-388.