Our results suggest that pSTAT3-S727 IHC staining could help distinguish ALK- ALCL from PTCL, NOS, even when CD30 is diffusely positive: if the H-score of pSTAT3-S727 expression surpasses 145, a diagnosis of ALK- ALCL is favorable. The gene discussed is ALK; the disease is mature T-cell and NK-cell non-Hodgkin lymphoma.