In fact, it is regarded as the signature of an aggressive clinical course with a poor prognosis in CD8+ TLGLL, characterized by CD56+/CD16–/CD57– LGLs, and aggressive NK cell leukemia, while it is devoid of negative prognostic significance in CD4+ T-LGLL and Tγδ LGLL. This evidence concerns the gene CD8A and aggressive NK-cell leukemia.