Metaplastic carcinoma of the breast: Prognosis and response to systemic treatment in metastatic disease

Background: Metaplastic breast carcinomas (MpBCs) are rare, aggressive breast cancers. Due to the scant literature of this disease most guidelines do not give recommendation for this entity. The aim of the study was to review the clinicopathologic features, treatment, and outcomes of the patients with MpBC treated at our institution. Material and methods: We searched databases for patients with histologically confirmed MpBC from 2002 to 2016. Results: A total of 78 patients with MpBC were included in the study. All histological material was reviewed by an experienced breast pathologist. Most tumors were grade 3 (83%) and triple negative (85%). Eighty-two percent were node negative. Sixty-four percent received adjuvant chemotherapy. The 5-year disease free survival was 63% and 5-year breast cancer specific overall survival was 61%. Tumor size and mixed metaplastic histology were associated with worse outcome in this patient group. One third of the patients (n = 28) had metastatic disease at initial presentation or developed metastases at follow-up. The lungs were the most common site of first distant recurrence. Half (n = 14) of these patients received palliative chemotherapy. Of those only 6% (n = 2) had partial response and 18% had stable disease as best response to treatment. The median overall survival time with metastatic disease was only 3.4 months. Conclusion: MpBC is an aggressive type of breast cancer with poor outcome despite low nodal involvement and aggressive local and systemic therapy. Tumor response to palliative systemic chemotherapy remains poor for MpBC patients.