Nagai et al. [56] report that ATLL is sustained by a small population of transformed CD4+ CCR7+ CD45RA+ CD45RO− CD95+ T memory stem (TSCM) cells, a unique population with stem cell-like properties, whereas the majority of ATLL cells are CD45RA− CD45RO+ conventional memory T cells. Here, CD4 is linked to adult T-cell leukemia/lymphoma.