The investigators believe that an operationally simple, cost effective, contrast enhanced mammogram (CEM), performed during the patient's diagnostic evaluation, would be the best approach to improve the accuracy of radiologists' decisions for need to biopsy lesions classified with mammography, tomosynthesis (DBT) or ultrasound as 4A or 4B. CEM uses iodine contrast with dual low and high KeV mammogram images to create a contrast enhancement map of the breast that directly overlays the mammogram, thus providing anatomic and kinetic information, similar to MRI. The investigators found in a preliminary clinical trial that radiologists had higher true-positive rates and lower false-positive rates for biopsy recommendation with CEM than when using DBT and ultrasound. To validate those initial findings, the investigators propose to prospectively and sequentially perform CEM on 1855 consenting women with BIRADS 4A or 4B lesions detected on mammography, DBT or ultrasound. Prospectively radiologists will provide BIRADS ratings for every lesion using DBT alone, then with ultrasound and finally with CEM. With pathology known and based on the study design to minimize case by radiologist potential biases, the investigators plan to estimate the NPV level of CEM-based recommendations (overall and within the cases with conventionally confirmed biopsy recommendation) and demonstrate that it is sufficiently high, while leading to substantial reduction in biopsy recommendations for actually benign lesions. The investigators primary expectation is that the number of recommendations to biopsy benign lesions will decrease significantly (\~20%), while maintaining high NPV (\>95%) among the initial recommendations.
