Clinicopathological and Imaging Features Predictive of Clinical Outcome in Metaplastic Breast Cancer

Background: Metaplastic breast cancer (MC) is a rare disease, thus it is difficult to study its clinical outcomes. Objective: To investigate whether any clinicopathological or imaging features were associated with clinical outcome in MC. Methods: We retrospectively evaluated the clinicopathological and imaging findings, and the clinical outcomes of seventy-two pathologically confirmed MCs. We then compared these parameters between triple-negative (TNMC) and non-TNMCs (NTNMC). Results: Oval or round shape, and not-circumscribed margin were the most common findings on mammography, ultrasound (US), and magnetic resonance imaging (MRI). It was mostly a mass without calcification on mammography, and revealed complex or hypoechoic echotexture, and posterior acoustic enhancement on US, and rim enhancement, wash-out kinetics, peritumoral edema, and intratumoral necrosis on MRI. Of all 72, 64 were TNMCs, and eight were NTNMCs. Clinicopathological and imaging findings were similar between the two groups, except that MRI showed peritumoral edema more frequently in TNMCs than NTNMCs (p=0.045). There were 21 recurrences and 13 deaths. Multivariable analysis showed that larger tumor size and co-existing DCIS were significantly predictive of Disease free survival (DFS), and larger tumor size and neoadjuvant chemotherapy were significantly predictive of overall survival (OS). Conclusion: MC showed characteristic imaging findings, and some variables associated with survival outcome may help to predict prognosis.