Breast tumors: comparative accuracy of MR imaging relative to mammography and US for demonstrating extent.

PURPOSE: To evaluate the comparative accuracy of magnetic resonance (MR) imaging relative to mammography and ultrasonography (US) for assessing the extent of breast tumors.

MATERIALS AND METHODS: Histologic results and preoperative imaging findings (mammography, US, MR imaging) were analyzed regarding tumor size and multifocality of 61 tumors in 60 women undergoing mastectomy for carcinoma.

RESULTS: In 10% of cases, the index tumor was not seen at mammography. With US, 15% of the index tumors were not recognized, while MR imaging missed 2% of the index tumors. On mammographic and US images, tumor size was underestimated significantly (P < .005), by 14% and 18%, respectively, while MR imaging showed no significant difference in size compared with that found in a pathologic evaluation. Mammography showed 31% of the additional invasive lesions, while US showed 38% and MR imaging showed 100%.

CONCLUSION: MR imaging was the most accurate of the three preoperative imaging modalities in assessing the size and number of malignant lesions in the breast.