Among the stem cell markers, CD24 were expressed in all of the CTC clusters at varying levels, while 5/6 clusters were found to express high levels (>50 rpm) of CD44. It has been previously reported that CD44 homophilic interactions and subsequent CD44–PAK2 interactions mediate tumor cell aggregation42 and improve stemness, survival, and metastatic progression43,44. This evidence concerns the gene CD24 and neoplasm.