Classification of normal screening mammograms is strongly influenced by perceived mammographic breast density.

Introduction: To investigate how breast screen readers classify normal screening cases using descriptors of normal mammographic features and to assess test cases for suitability for a single reading strategy.

Methods: Fifteen breast screen readers interpreted a test set of 29 normal screening cases and classified them by firstly rating their perceived difficulty to reach a 'normal' decision, secondly identifying the cases' salient normal mammographic features and thirdly assessing the cases' suitability for a single reading strategy.

Results: The relationship between the perceived difficulty in making 'normal' decisions and the normal mammographic features was investigated.