In the course of our GEP study, we found that all ALCL tended to cluster together irrespective of their ALK status, and this signature was clearly distinct from that of PTCL/NOS.20 In addition to suggesting that ALK-positive and ALK-negative ALCL probably share a set of deregulated pathways, our findings did not support the proposal that ALK-negative ALCL is a subtype of PTCL/NOS. This evidence concerns the gene ALK and mature T-cell and NK-cell non-Hodgkin lymphoma.