Fas, as a member of the death-inducing family of tumor necrosis factors (receptors with an intracellular death domain) can initiate the extrinsic apoptosis signaling pathway.[20] In the present case, Fas expression was not detected in the CD4+ ATLL, this might be associated with a reduction in the apoptosis rate and may be one of the reasons for the long-term survival of ATLL cells. This evidence concerns the gene CD4 and adult T-cell leukemia/lymphoma.