ObjectiveTo investigate the effect of extranodal extension of axillary lymph nodes metastasis on the prognosis of patients with triple-negative breast cancer (TNBC). MethodsThe TNBC patients with axillary lymph node metastasis admitted to the Nanyang Central Hospital from January 2017 to January 2019 were collected. The clinicopathologic characteristics and prognosis of TNBC patients with or without extranodal extension were analyzed and compared, and the factors affecting prognosis were analyzed. ResultsA total of 216 patients were included, including 123 patients without extranodal extension and 93 patients with extranodal extension. Compared with the patients without extranodal extension, the proportions of the patients with histological grade Ⅲ, 10 or more metastatic lymph nodes, and 5 cm or greater tumor diameter were higher in the patients with extranodal extension (P<0.05). The results of multivariate analysis showed that the 10 or more metastatic lymph nodes was the risk factor affecting the overall survival (OS) and disease-free survival (DFS) of the TNBC patients (P<0.05), and the histological grade Ⅲ and lower human epidermal growth factor receptor-2 (HER-2) expression were the risk factors affecting the OS of the TNBC patients (P<0.05), as well as the extranodal extension was the risk factor affecting the DFS of the TNBC patients (P<0.05). The 5-year cumulative disease-free survival rate of the patients with extranodal extension was worse than that of the patients without extranodal extension (70.2% vs. 83.3%, χ2=6.934, P=0.008). The 5-year cumulative overall survival rate had no statistically significant difference between the them (75.3% vs. 82.1%, χ2=1.969, P=0.161). ConclusionsFrom the results of this study, the prognosis of TNBC patients with extranodal extension is worse. Especially the patients with histological grade Ⅲ, 10 or more metastatic lymph nodes, and with lower HER-2 expression should be paid attention.