The detection of breast cancer involves the screening of breast tissues thought to be normal.  The x-ray image of the breast exhibits a pattern within a spectrum of "normal variation."  Mammographic interpretation involves careful scrutiny of this "normal pattern" and any abnormalities which present itself as a disruption of the "normal pattern."

The first step is to compare the right breast to the left breast on the current examination.  Since the breasts are seen as symmetric organs,  if the mammograms are viewed using symmetric placement on a viewbox, the architecture and distribution of density should be close to mirror images.

Viewing the mammogram should proceed from a distance to closer scrutiny of the particular suspicious areas.  From a distance, the images should be compared area for area, and the respective regions of the left and right breasts should look similar.  One should have both images in view whereby the contour of the breast, the size of the breast, and its symmetric density could be evaluated.  This bird's eye evaluation for symmetry is followed by a close-up individual view of each image, looking for disruption in the "normal pattern" of the breast such as abnormal densities, areas of architectural distortion, masses and calcifications. 

If there are prior mammograms available for review, the individual breasts are evaluated for changes over time.  The goal here is to look for potential changes in asymmetric density as well as to evaluate development of new masses (neodensities) or new calcifications. However, if the present study is unremarkable, prior mammograms are of lesser importance.

Soft tissue lesions found within a mammogram often will have distinguishing shape, size, and margin characteristics. Likewise, calcifications can be characterized by their size, number, morphology, distribution, and heterogeneity. These distinguishing characteristics are the basis upon which the interpretation of a mammogram may be classified as benign, malignant, or equivocal. The several subsections of  Tutorial 2  present an introduction to the mammographic appearance of normal and abnormal breast tissues.