Factors associated with discordance between pathological and radiological tumor size and risk of re-excision in breast-conserving surgery: a post-hoc analysis within a randomized trial.

Among 414 patients (median age 65 years; median tumor size 10.3 mm), MRI was performed in 24.4%.

Median Pathology-to-Radiology Ratio was 1.25, suggesting systematic underestimation.

MRI consistently overestimated tumor size in most subtypes but provided more accurate estimates for invasive lobular carcinoma (invasive lobular carcinoma), compared with conventional imaging.

Independent predictors of discordance included invasive lobular carcinoma, high grade, and small tumor size.