Metaplastic breast cancer: a comparison between the most common histologies with poor immunohistochemistry factors

Background: Metaplastic carcinoma of the breast (MCB) is a rare histological type of breast cancer. This study aimed to determine whether MCB exhibits shorter overall survival (OS) and disease-free survival (DFS) compared with other histologies that are considered unfavorable. Methods: We retrospectively analyzed 157 clinical file records of the Mexico City-based National Institute of Cancerology and compared the clinical characteristics and treatment of 24 patients with MCB, 37 patients with triple-negative invasive lobular carcinoma (TN-ILC), 48 patients with high-grade invasive ductal carcinoma (HG-IDC), and 48 patients with triple-negative invasive ductal carcinoma (TN-IDC), paired by clinical stage and age. We performed a comparative analysis and analyzed OS and DFS using a log-rank test. Results: In patients with MCB, the 5-year DFS was 52.1% (mean, 48.52 months; 95%: 35.32-61.72), and the 5-year OS was 72.2% (mean, 59.77 months; 95% CI: 48.55-71.00). No differences were observed in the DFS of MCB compared with each of the other histologies (MCB vs. HG-IDC, p = 0.865; MCB vs. TN-IDC, p = 0.966, and MCB vs. TN-ILC, p = 0.132). Moreover, no differences were observed when comparing the OS of MCB with that of each of the other histologies (MCB vs. HG-IDC, p = 0.246; MCB vs. TN-IDC, p = 0.255, and MCB vs. TN-ILC, p = 0.387). Conclusions: Neither OS nor DFS differ between patients with MCB and those with other histologies with unfavorable immunohistochemical factors.