CD5 and B-cell chronic lymphocytic leukemia: Research on compartmental trafficking indicates that CLL cells actively proliferating within the bone marrow or lymph node niches exhibit upregulation of CD5 and downregulation of CXCR4, leading to the formation of the CD5highCXCR4low subset, referred to as recent stromal-niche emigrants (RSEs).23 Once these cells migrate into peripheral blood, they transition into a quiescent state, reduce their proliferative activity, downregulate CD5, and restore CXCR4 expression,24 resulting in the CD5lowCXCR4high subset, known as long-term circulating cells (LTCs).