In the case of Sezary syndrome, a phenotype of central memory CD4 T lymphocytes (CD45RA− CD45RO+ CCR7+ CD27+, and CD62L+/−) is characteristic, unlike mycosis fungoides where its immunophenotype profile is that of an effector memory cell that is resident in the skin (CD45RA− CD45RO+ CCR7− CD27−, and CD62L−). This evidence concerns the gene CCR7 and mycosis fungoides.