Interpreting one-view mammographic findings: minimizing callbacks while maximizing cancer detection.

Overlap of breast tissue is a frequent consequence of the necessary positioning and compression of the three-dimensional breast to obtain two-dimensional mammograms. The mammary glands contain fewer anatomically fixed landmarks than solid organs do; thus, variability in positioning can have an even greater effect on mammography than it has on other imaging examinations. Most often, areas of overlapping fibroglandular tissue, also known as summation shadows, are seen on only one of the two standard mammographic views. While striving to detect breast cancer as early as possible, radiologists must learn to visually compensate for apparent abnormalities in the breast that are produced by such tissue overlap. Mammographic interpretation in this setting is made even more challenging by the fact that the only manifestation of breast cancer might be a subtle change on a single mammographic view. Breast cancer might be obscured on one of the two standard views because of the density of surrounding breast tissue, mammographic technique, lesion size or location within the breast, histopathologic characteristics of the tumor, or lack of effect by the tumor on the appearance of surrounding tissues. To heighten awareness of the factors that can lead to either unnecessary recalls or failure to identify breast cancer, cases are reviewed in which false-positive findings and breast cancers were visible on only one mammographic view. Strategies for interpreting screening mammograms and determining which findings merit diagnostic evaluation are outlined so as to help minimize false-positive findings and aid in cancer detection.