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Research Article: Metaplastic breast carcinoma versus triple-negative breast cancer: distinct metastatic patterns and inferior overall survival in a matched retrospective cohort study

Date Published: 2026-09-22

Abstract:
Metaplastic breast carcinoma (MBC) is an uncommon invasive breast cancer subtype with marked morphological diversity. Many MBCs are managed within the triple-negative breast cancer (TNBC) framework, yet their clinical course may not mirror that of non-metaplastic TNBC. We therefore compared clinicopathological features, recurrence and metastatic patterns, and survival outcomes in patients with MBC and those with non-metaplastic TNBC. We reviewed 27 patients with pathologically confirmed MBC who were treated at the Cancer Hospital of Ningxia Medical University General Hospital from January 2015 to December 2023. From patients with non-metaplastic TNBC treated in the same period, 81 controls were randomly selected at a 1:3 ratio and matched by age and year of diagnosis. We assessed clinicopathological variables, immunohistochemical findings, treatment patterns, recurrence and metastasis, disease-free survival (DFS), and overall survival (OS). Survival was evaluated with Kaplan-Meier curves and log-rank tests. The two cohorts were comparable in age and menopausal status. Relative to TNBC, MBC more often presented as grade III disease (88.9% vs. 28.7%, P < 0.001) and T3–T4 disease (33.3% vs. 11.1%, P = 0.007), while nodal involvement was less common (25.9% vs. 51.9%, P = 0.019). Proliferative activity was greater in MBC, with a higher Ki-67 index (54.0 ± 16.3% vs. 43.5 ± 22.0%, P = 0.011) and a higher proportion of tumors with Ki-67 ? 30% (100.0% vs. 81.5%, P = 0.020). During follow-up, recurrence or metastasis (25.9% vs. 8.6%, P = 0.041) and distant metastasis (22.2% vs. 2.5%, P = 0.003) occurred more often in MBC. DFS was numerically shorter in MBC but was not statistically different ( P = 0.200), whereas OS was significantly poorer ( P = 0.038). In this matched cohort, MBC showed a profile of high-grade histology, greater tumor burden, active proliferation, limited nodal spread, and frequent distant metastasis. The results indicate that MBC should not be treated simply as another presentation of TNBC, but as a high-risk entity requiring careful assessment of metastatic risk.

Introduction:
Metaplastic breast carcinoma (MBC) is an uncommon invasive breast cancer subtype with marked morphological diversity. Many MBCs are managed within the triple-negative breast cancer (TNBC) framework, yet their clinical course may not mirror that of non-metaplastic TNBC. We therefore compared clinicopathological features, recurrence and metastatic patterns, and survival outcomes in patients with MBC and those with non-metaplastic TNBC.

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