CD4 and mature T-cell and NK-cell non-Hodgkin lymphoma: The authors showed that PTCL/NOS are most closely related to activated peripheral T lymphocytes, either CD4+ or CD8+, based on the GEP. In addition, PTCL/NOS displayed deregulation of relevant functional cell programmes. In particular, among others, PDGFRA, a gene encoding for a tyrosine kinase receptor, turned out to be aberrantly expressed by PTCL/NOS. Notably, phosphorylation of PDGFRA and sensitivity of cultured PTCL cells to imatinib were demonstrated.