Clinicopathological characteristics and prognostic analysis of tumor-infiltrating lymphocytes (TILs) in ductal carcinoma in situ (DCIS) and DCIS with microinvasion (DCIS-Mi) of the breast

Objective Our purpose is to evaluate the correlation of TILs with clinicopathological characteristics and disease free survival (DFS) in DCIS and DCIS-Mi breast cancer (BC) patients. Methods We retrospectively reviewed the data of 360 DCIS patients and 125 DCIS-Mi patients treated by a single institution from 2016 to 2019. TILs are regarded as continuous variables and are divided into low (≤ 5%), medium (5–40%) and high (≥ 40%) for statistical analysis. Results In DCIS and DCIS-Mi patients, larger tumor size, higher nuclear grade, hormone receptor (HR) negativity and human epidermal growth factor receptor 2(HER2) overexpression are all related to high TILs ( P < 0.05). In addition, compared with DCIS, DCIS-Mi patients were significantly associated with high TILs ( P < 0.001). Based on the different results of the subtypes, we further studied the correlation between TILs and DFS in 279 cases of HER2+ patients (204 of DCIS; 75 of DCIS-Mi). In HER2+ group, DCIS-Mi was significantly associated with HR negativity ( P = 0.015) and high TILs ( P = 0.002) compared with DCIS patients. In the survival analysis, we found that TILs had no effect on the DFS of DCIS ( P = 0.938), DCIS-Mi ( P = 0.807), and HER2+ ( P = 0.379) BC patients. In the univariate and multivariate cox regression analysis, the correlation between TILs and the prognosis of DFS has not been confirmed in the three BC groups ( P > 0.05). Conclusion TILs have played an non-negligible role in the progress of DCIS to DCIS-Mi, especially in HER2+ BC. The predictive and prognostic value of TILs still needs further research to confirm.