The usefulness of preoperative MRI in synchronous bilateral breast cancer

Background: The incidence of synchronous bilateral breast cancer is increasing each year. The applicability of contrast-enhanced magnetic resonance imaging (MRI) in the detection of multiple breast lesions has been reported in many studies. However, there have been no reports concerning the usefulness of preoperative MRI to evaluate synchronous bilateral breast cancer in Japan. We reviewed patients with synchronous bilateral breast cancer to investigate the applicability of contrastenhanced MRI in detecting contralateral breast cancer that was not visible by MMG or ultrasound. Methods: Synchronous bilateral breast cancer was found in 47 (3.2%) of the 1465 breast cancer patients who underwent surgery in our hospital between April 2006 and December 2012. Of those 47 patients, we enrolled 28 patients whose second lesions were non-palpable. The sensitivities of MMG, ultrasonography, and contrastenhanced MRI were compared for their ability to detect the malignancy of the second lesion. We also assessed the pathological characteristics of those lesions that were only visible by contrast-enhanced MRI. Results: In 28 patients whose second lesions were non-palpable,7% was DCIS in first lesions, and 39% was DCIS in second lesions. The median size of the invasive cancer was 2.3 cm (range, 0.5-9.5 cm) within the first lesions. The median size of the invasive cancer was 1.0 cm (range, 0.4-5.0 cm) within the second lesions. Of the 28 malignant lesions, 13 (46%) were positive by MMG, 18 (64%) were positive by ultrasonography, and 28 (100%) were positive by contrast-enhanced MRI. In six of the 28 patients (21%), the malignant lesions were found by contrast-enhanced MRI but not by MMG nor by ultrasonography. Conclusion: Contrast-enhanced MRI has the highest sensitivity and is therefore the most useful modality in identifying non-palpable breast abnormalities. It is especially useful in the detection of small contralateral lesions and lesions immediately under the nipple of the contralateral breast. Correspondence to: Yoshimasa Kosaka, Department of Surgery, School of Medicine, Kitasato University, 1-15-1 Kitasato, Minami-ku, Sagamihara, Kanagawa, Japan; Tel: +81 427788111, Fax: +81 427789556; E-mail: y-kosaka@med.kitasato-u.ac.jp