ObjectiveTo investigate the effect of extranodal extension of axillary lymph nodes on the prognosis of 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, and the patients were assigned into a negative soft tissue group and positive soft tissue group according to the status of soft tissue of external lymph node. The clinicopathologic characteristics and prognosis of the two groups were compared, and the factors affecting the prognosis were analyzed. ResultsA total of 216 patients were included, 123 and 93 of whom were in the negative soft tissue group and positive soft tissue group, respectively. Compared with the patients in the negative soft tissue group, the patients in the positive soft tissue group had a higher proportion of higher histological grade (grade Ⅲ), more number of metastatic lymph node (10 or more), and greater tumor diameter (5 cm or more), P<0.05. The 5-year cumulative disease-free survival (DFS) rate of the negative soft tissue group was higher than that of the positive soft tissue group (83.3% vs. 70.2%, χ2=? , P=0.008). The 5-year cumulative overall survival (OS) rate had no statistically significant difference between the the negative soft tissue group and positive soft tissue group (82.1% vs. 75.3%, χ2=? , P=0.161). The results of multivariate analysis showed that the higher histological grade (grade Ⅲ) and extranodal extension of axillary lymph nodes were the risk factors affecting the OS and DFS of the TNBC patients (P<0.05). It was also found that the number of metastatic lymph nodes (10 or more) and higher HER-2 expression were the risk factors affecting the OS of the TNBC patients (P<0.05), but which were not related to the DFS of the TNBC patients (P>0.05). ConclusionThe prognosis of TNBA patients with extranodal extension of axillary lymph nodes is worse, especially those with histological grade Ⅲ, lymph node metastasis number >10, and higher HER-2 expression.