Is there concordance of invasive breast cancer pathologic tumor size with magnetic resonance imaging?

Background: In the era of breast conservation therapy, preoperative imaging is imperative in planning a single definitive surgical treatment. Methods: We performed a retrospective review of a prospectively collected database of patients treated at a single institution for invasive breast cancer over 5 years. Clinical and pathologic variables were analyzed with respect to magnetic resonance imaging (MRI) and pathologic tumor size using analysis of variance F tests and chi-square tests. Results: Of 190 patients, 53% had concordance of MRI and pathologic cancer size within .5 cm. MRI overestimated 33% and underestimated 15% of tumors. Neoadjuvant chemotherapy and lymph node status were associated with discordance. Among tumors overestimated by MRI, 65% had additional significant findings in the breast tissue around the main lesion: satellite lesions, ductal carcinoma in situ, and/or lymphovascular invasion. Conclusions: Breast MRI is concordant with pathologic tumor size within .5 cm among 53% of patients. Most patients with tumors overestimated by MRI have significant findings in the surrounding breast tissue, the excision of which would be expected to benefit the patient.