Figure 1a. Mammograms obtained in 61-year-old woman show a BI-RADS 1 lesion seen at unblinded rereview with CAD output. Normal-appearing (a) craniocaudal and (b) mediolateral-oblique screening mammograms obtained 13 months prior to diagnosis of a 1.2-cm, grade II invasive ductal carcinoma are shown. When the location of the subsequently developing cancer is noted, in retrospect, there is a focal island of normal tissue in the lower part of the right breast that was interpreted as normal by the two breast imaging specialists at unblinded review. (c) Craniocaudal view subsequently obtained at the time of cancer diagnosis shows an oval obscured mass (arrow) in the outer part of the right breast that is denser than the tissue seen in a. (d) Mediolateral oblique view obtained at the time of cancer diagnosis shows the same mass (arrow) in the lower part of the right breast. (e) CAD output shows low-spatial-resolution mammograms (from left to right: right craniocaudal, left craniocaudal, right mediolateral-oblique, left mediolateral-oblique views) and marked findings. The CAD system marked the focal island of tissue (*) on only the right mediolateral-oblique view (left image on right side) of the prior normal mammograms in a and b. The CAD system also marked benign-appearing calcifications (
) in the upper part of the right breast on the right mediolateral-oblique view (left image on right side). The CAD system marked skin calcifications () and a region of glandular tissue (*) in the outer part of the left breast on the left craniocaudal view (right image on left side). Note that the finding where cancer later developed is seen on only one view (right mediolateral-oblique) and looks like normal tissue.