Breast cancer stem cells phenotype and plasma cell-predominant breast cancer independently indicate poor survival

Cancer stem cell-tumor microenvironment ecosystem is proposed to drive tumor heterogeneity. Tumor-infiltrating lymphocytes (TILs) in breast cancer ecosystem were demonstrated to indicate better prognosis and benefit from chemotherapy. This study sought to detect the association between breast cancer stem cells and TILs. 92 patients with breast cancer were enrolled. Matched cancerous and paracancerous tissues were assembled in a tissue microarray and immunohistochemistry was employed to test expression of breast cancer stem cells (BCSCs) markers. TILs counts were estimated with global hematoxylin-eosin staining. The association between TILs and BCSCs phenotypes was analysed by multivariate analysis. Although it was unable to find direct significant association between BCSCs phenotypes and TILs, the BCSCs phenotype with CD44+CD24−ALDH1A1+EpCAM+CD49f+ was proved to be associated with worse DFS and OS (P=0.037 and 0.001). This result was confirmed by cox proportional-hazards regression model (for DFS and OS respectively, HR=2.438 and 3.383, P=0.019 [95%CI 1.418–3.457] and 0.025 [95%CI 1.162–9.843]). Additionally, in results of TILs, plasma cell-predominant breast cancer (PPBC) was unexpectedly found to indicate worse OS and HR was 2.686 (P=0.038 [95%CI 1.582–3.789]). The BCSCs phenotype and PPBC may be helpful stratified factors in future clinical trials. The underlying mechanism needs further research.