Efficacy of step-oblique mammography for confirmation and localization of densities seen on only one standard mammographic view

OBJECTIVE. Step-oblique mammography is a technique used to determine with c onfidence whether a mammographic finding visible on multiple images on only one projection (but not elucidated using standard additional mammographic projections such as the roll view) represents a summation artifact or a tru e mass. and to precisely localize the true mass for further evaluation (if applicable). This paper describes the step-oblique technique and evaluates its efficacy. MATERIALS AND METHODS. Between January 1, 1993 and December 31, 1998, 69 co nsecutive women underwent step-oblique mammography for the evaluation of de nsities seen on multiple images in only one standard projection. Additional images were obtained at 15 degrees stepped increments in obliquity. If a o ne-projection-only finding was not seen on step-oblique images, the density was judged to represent a summation artifact, completing the examination. If a density was visualized and could be triangulated concordantly on step- oblique images ranging from the craniocaudal to the 90 degrees lateral proj ection, then it was judged to represent a real lesion. Such a lesion was fu rther characterized (mass, neodensity, architectural distortion, focal asym metric density) and was localized precisely in three dimensions, permitting imaging-guided tissue diagnosis, if appropriate. For all study patients, w e also recorded BI-RADS (American College of Radiology Breast Imaging and D ata Reporting System) assessment categories, pathology results for biopsied lesions; and mammographic follow-up, clinical follow-up, and linkage to re gional tumor registry for nonbiopsied lesions for which at least 2 years ha d elapsed since step-oblique mammography. RESULTS. Step-oblique mammography differentiated 50 real lesions from 19 su mmation artifacts. All 50 real lesions, although initially visible on only one standard projection, were successfully localized in three dimensions. S ubsequent management resulted in the prompt detection and diagnosis of seve n breast cancers and 21 benign lesions. None of the remaining findings mana ged by follow-up rather than biopsy have subsequently been found to be mali gnant. CONCLUSION. Step-oblique mammography is an effective means of evaluating th e mammographic finding visible on multiple images on only one standard proj ection.