Metaplastic carcinoma (MPC) is a rare subgroup of breast tumours accounting for <5% of all invasive breast cancers. Histologically confirmed 40 MPC from January 2001 to December 2018 were identified from our electronic database: stage I 2.5% (n = 1), stage II 40% (n = 16), stage III 45% (n = 18) and stage IV 12.5% (n = 5). The mean tumour size was 6 cm, node-negative in 60%, and hormone receptor-negative in 75%. Among the 35 non-metastatic patients, 17 (48.6%) received initial neoadjuvant treatment (NAT), followed by surgery, and only 1 had a complete pathological response. At a median follow-up of 60 months, 17% (n = 6) had a recurrence. All six of them had lung metastasis. The 5-year overall survival (OS) and disease-free survival were 64.4% and 66.3%, respectively. Age more than 46 years (p = 0.027), tumour size more than 5 cm (p = 0.037), and nodal positivity (p = 0.001) were predictors of OS. In node-positive patients, the 5-year OS in those who underwent initial surgery was 80% and after NAT was 21.4% (p = 0.069). In node-negative patients, the 5-year OS after initial surgery was 83.3% and after NAT was 90% (p = 0.380). A statistical significance could not be demonstrated due to the small number of patients. Due to chemoresistance, the concept of initial NAT in MPC of the breast is a subject to be studied in the future. Upfront surgery should be considered for operable diseases (including stage III), followed by a decision on adjuvant therapy. Optimal treatment and effective systemic therapy regimens are yet to be defined.
Keywords: chemoresistance; metaplastic carcinoma; node-positive; receptor negative; triple negative.
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