Clinical and Pathologic Features of Clinically Occult Synchronous Bilateral Breast Cancers

Purpose: To investigate clinicopathologic breast cancer characteristics associated with the identification of synchronous bilateral breast cancer (SBBC) on dynamic contrast-enhanced breast magnetic resonance imaging. Methods: We performed a retrospective review of 311 consecutive patients newly diagnosed with breast cancer who underwent diagnostic mammography, ultrasonography, and dynamic contrast-enhanced breast magnetic resonance imaging (DCE-MRI) at our institution. Tumor histology, grade, biomarker status (estrogen receptor, progesterone receptor, and HER2), TNM staging, and unifocal or multifocal/multicentric status were compared between the index tumors in the unilateral disease and the SBBC groups, as well as between the index tumors in the unilateral disease group and the synchronous contralateral tumors (SCT) in the SBBC group, using the Fisher exact test. Results: A total of 326 cancers in 311 patients were reviewed. Fifteen (4.8%) patients were diagnosed with SBBC. The index tumors in patients with SBBC were more frequently lower T stage (p = 0.007), lower grade (p = 0.04), and multifocal/multicentric (p = 0.004) compared with the index tumors in the unilateral group. Biomarkers, N status, and M status did not significantly differ between the index tumors in both groups. Conclusions: SBBC was more likely to be identified in women with lower T stage, lower tumor grade and multifocal/multicentric tumors. Multimodality imaging including DCE-MRI is essential in detection and diagnosis of SBBC.