Abstract
OBJECTIVE: To determine prevalence and frequency of malignancy among bone lesions detected on breast MRI and to identify clinical and imaging features associated with bone metastases from breast cancer (BC), as bone lesions are suboptimally evaluated on breast imaging protocols and can present a diagnostic challenge. METHODS: This IRB-approved retrospective review of breast MRIs performed from June 2009 to June 2018 identified patients with bone lesions. Demographic, clinical, and MRI features were reviewed. Clinical outcome of bone lesions was determined based on pathology and/or additional diagnostic imaging. All benign lesions had ≥ 2 years of imaging follow-up. Statistics were computed with Fisher's exact and Wilcoxon rank sum tests. RESULTS: Among all patients with breast MRI, 1.2% (340/29 461) had bone lesions. Of these, 224 were confirmed benign or metastatic BC by pathology or imaging follow-up, with 70.1% (157/224) be- nign and 29.9% (67/224) metastatic. Bone metastases were associated with BC history (P < 0.001), with metastases occurring in 58.2% (53/91) of patients with current BC, 17.9% (14/78) patients with prior BC, and 0.0% (0/55) without BC. Bone metastases were associated with invasive and ad- vanced stage BC and, on MRI, with location in sternum, ribs, or clavicles, larger size, multiplicity, andT1 hypointensity (all P < 0.01 in tests of overall association). CONCLUSION: Of clinically confirmed breast MRI-detected bone lesions, 30% were bone metastases; all were detected in patients with current or prior BC. Metastases were associated with advanced stage, invasive carcinoma, larger lesion size, multiplicity, low T1 signal, and non-spine location.