The WHO-HAEM5 and the International Consensus Classification (ICC) both characterize adult T-cell leukemia/lymphoma (ATLL) as a type of peripheral T-cell cancer originating from CD4-positive T-cells infected with human T-cell leukemia virus (HTLV) type 1 [49,50]. This evidence concerns the gene CD4 and adult T-cell leukemia/lymphoma.