According to this study, PTCL/NOS could be divided into three molecular subgroups: U1, U2 and U3. The U1 gene expression signature included genes known to be associated with poor outcome in other tumours, such as CCND2. The U2 subgroup was associated with overexpression of genes involved in T cell activation and apoptosis, including NF-κB1 and BCL-2. The U3 subgroup was mainly defined by overexpression of genes involved in the IFN/JAK/STAT pathway. Notably, such distinction possibly reflected, at least in part, the presence of reactive components in the PTCL samples. This evidence concerns the gene IFNA1 and mature T-cell and NK-cell non-Hodgkin lymphoma.