Jingwei Liu, Nan Zhang, Xiujie Yu, Rui Feng, Hong Liu
Triple-negative ductal carcinoma in situ (TN-DCIS) is uncommon, and its prognostic significance remains unclear. We aimed to characterize the clinicopathological features of TN-DCIS and evaluate its association with recurrence outcomes. We retrospectively reviewed patients with pathologically confirmed pure DCIS treated at Tianjin Central Hospital of Gynecology Obstetrics between January 2008 and December 2021. Patients with microinvasive or invasive carcinoma were excluded. Patients were classified as TN-DCIS or non-TN DCIS according to immunohistochemistry. The primary endpoint was disease-free survival (DFS). Secondary endpoints included ipsilateral breast tumor recurrence (IBTR)-free survival, invasive recurrence-free survival, and time to invasive recurrence. Survival outcomes were estimated using Kaplan–Meier methods and compared with log-rank tests. Cox regression was used to explore factors associated with DFS. Among 111 patients, 13 (11.7%) had TN-DCIS and 98 had non-TN DCIS. Within 5 years of follow-up, DFS events occurred in four patients with TN-DCIS and one patient with non-TN DCIS. The corresponding 5-year DFS rate was lower in the TN-DCIS group than in the non-TN DCIS group (69.23% [95% CI, 48.19–99.47] vs. 98.98% [95% CI, 97.01–100.00]; p < 0.001). In exploratory multivariable Cox analysis, TN-DCIS was associated with poorer DFS (HR 5.990, 95% CI, 1.686–21.280; p = 0.0056). Breastfeeding history was associated with lower recurrence risk (HR 0.123, 95% CI, 0.030–0.513; p = 0.004), whereas CK5/6 positivity was associated with increased recurrence risk (HR 5.525, 95% CI, 1.302–23.451; p = 0.0205). TN-DCIS was also associated with poorer 5-year IBTR-free survival and invasive recurrence-free survival, with similar exploratory findings observed in the breast-conserving surgery subgroup. TN-DCIS was uncommon but associated with increased recurrence risk. The triple-negative phenotype may identify a clinically higher-risk DCIS subgroup. These findings warrant validation in larger multicenter cohorts and future evaluation of tailored surveillance strategies.