In addition to expression in most CD4+CD25+ ATLL, CCR4 is expressed in approximately 30–65% of PTCL tumor cells, including high expression (~ 65%) in ALK-negative ALCL, variable expression (30–40%) in PTCL/NOS, AITL, and transformed MF, while rarely expressed in ENKTL or ALK-positive ALCL [25]. Here, CD4 is linked to adult T-cell leukemia/lymphoma.