Benign Lesions on Screening Mammography: Increasing Diagnostic Confidence in a Hitherto Unscreened Population.

INTRODUCTION: Screening mammography is used for detection of breast cancer and is interpreted using the Breast Image Reporting and Data System (BIRADS) convention. It is not routinely offered to women in countries which do not have a national screening programme resulting in a challenge for the radiologist who has to interpret these in the absence of previous mammograms. AIM: To analyse benign and probably benign lesions in screening mammograms in a hitherto unscreened population and suggest protocols to increase diagnostic confidence.
MATERIALS AND METHODS: Screening mammograms of 362 asymptomatic women in the age range of 40 to 60 years carried out over a two year period were retrospectively analysed. Patients of breast cancer and those who had palpable lumps were excluded from the study. All images were analysed in standard Mediolateral Oblique (MLO) and Craniocaudal (CC) projections with additional views wherever necessary. Corroborative ultrasound had been carried out wherever indicated in the opinion of the interpreting radiologist. The mammograms were finally classified according to the BIRADS convention.
RESULTS: Of the total number of 362 women screened, most of whom did not have any previous mammogram, 162 were reported as BIRADS I, 179 as BIRADS II and 18 as BIRADS III. The mammograms reported as BIRADS II had various findings including dystrophic calcification/macrocalcification, vascular calcification, simple cysts and fibroadenomas. Only 26 (16.04%) of the BIRADS I mammograms had undergone further evaluation with Ultrasound (US) due to dense breasts or asymmetrical involution of breast tissue whereas 76 (42.5%) of the BIRADS II mammograms had undergone further evaluation with US to characterize lesions like cysts and fibroadenomas, but occasionally also for benign clustered calcification. Of BIRADS III mammograms, 12 (66.6%) had required US correlation to exclude a mass in cases with dense breasts. The increased likelihood of ultrasound corroboration in BIRADS II and BIRADS III was analysed using the Chi square test and was statistically significant.
CONCLUSION: In the absence of previous screening mammograms, a small number of BIRADS I mammograms and a significant number of BIRADS II and BIRADS III mammograms undergo a corroborative US examination. The addition of supplemental US to the evaluation of these lesions increase diagnostic confidence and lesion characterization in a population which is not subject to routine screening.