Survival Outcomes in Metaplastic Versus Triple-Negative Invasive Breast Carcinoma: A Propensity Score-Matched Study

Background and Objectives: Metaplastic breast carcinoma (MBC) is a rare, predominantly triple-negative breast cancer subtype with aggressive clinical behaviour. This study compared the clinicopathological characteristics and survival outcomes of MBC with triple-negative invasive breast carcinoma (TN-IBC) and assessed the prognostic value of the neutrophil-to-lymphocyte ratio (NLR). Materials and Methods: Patients with stage I–III MBC or TN-IBC diagnosed between January 2003 and January 2024 were retrospectively reviewed. Among 35 patients with MBC and 103 with TN-IBC, 1:1 propensity score matching by age and TNM stage generated two groups of 35 patients. Disease-free survival (DFS) and overall survival (OS) were evaluated using Kaplan–Meier estimates and Cox proportional hazards models with robust sandwich variance clustered by matched pair. Results: All 70 matched patients had triple-negative disease. During a median follow-up of 7.7 years, recurrence occurred in 22.9% of patients with MBC and 17.1% of those with TN-IBC, while mortality rates were 25.7% and 8.6%, respectively. Five-year DFS rates were 73.9% and 85.2%, respectively; however, MBC was not significantly associated with DFS (HR = 1.70, 95% CI 0.67–4.30; p = 0.262). Five-year OS rates were 79.8% and 94.3%, respectively. Metaplastic histology was associated with a higher mortality hazard (HR = 3.53, 95% CI 1.01–12.41; p = 0.049). Median NLR was higher in MBC than in TN-IBC (2.31 vs. 1.85; p = 0.019). High NLR was associated with poorer OS in the overall matched cohort (HR = 3.36, 95% CI 1.07–10.57; p = 0.038), although NLR was not significantly associated with survival when analysed as a continuous variable or within the MBC subgroup. Conclusions: MBC was associated with inferior OS compared with TN-IBC after propensity score matching and pair-adjusted survival analysis, while DFS did not differ significantly. Elevated NLR was associated with poorer OS in the overall matched cohort but was not validated as an MBC-specific prognostic biomarker.