PRF1 and aggressive NK-cell leukemia: Abnormal NK cells in ANKL were found to have a distinctiveCD56bright/CD16dim immunophenotype and markedly increased Ki-67 expression, whereas CD57 negativity and reduced expression of killer immunoglobulin-like receptor (KIR), CD161, CD7, CD8 and perforin were exhibited compared with other NK cell proliferative disorders (p<0.05).