CD44 and breast cancer: Thus, further studies are warranted with advanced cutting-edge technologies, such as combination of single-cell RNA-seq, multiple marker-based CyTOF mass cytometry or spatial proteomics to quantify the frequency or number of CD44-/CD24- breast cancer cells in fresh breast cancer tissues, together with prospectively following-up the patients, in a bigger population to investigate the prognostic value of CD44-/CD24- breast cancer cells and the molecular mechanisms underlying the spontaneous conversion of CD44-/CD24- TNBC into CD44+/CD24- CSCs in the metastasis of breast cancer.