Concise preoperative assessment of breast Tumor size is important when considering surgical approach and the staging of breast cancer. A retrospective study of 400 uni-focal, invasive ductal carcinomas compared the accuracy of sonographic and mammographic measuring modalities with histological size. Sub-groups for tumor size, type and grade, with other variables, were also considered in intra-modal correlations of lesion dimension. Mammography (R2=0.74), although slightly over estimating tumor size, appeared to be more useful than sonography (R2=0.60) following logistical analysis of the data. Correlational significance for both imaging modalities decreased for tumors larger than 20mm. Sonography under estimated lesions in over 50% of cases; the average underestimate being 9.9 mm, and ranging from 1mm to 30 mm. Consideration of both imaging measurements in cohort should improve the accuracy of radiological reporting of pre-surgical tumor size.