When narrowing down to differential diagnosis between ALK- ALCL and CD30high PTCL, NOS, considering a minority (13%) of ALK- ALCL expressing pSTAT3-Y705 in a very low level (<30%), pSTAT3-S727 appears to be a better choice, with a sensitivity of 0.86 and specificity of 0.9. This evidence concerns the gene ALK and mature T-cell and NK-cell non-Hodgkin lymphoma.