RTKs such as platelet-derived growth factor receptor A (PDGFRA), discoidin domain-containing receptor 2(DDR2),tyrosine kinase receptor A (TRKA) and TRKB showed to be aberrantly expressed in HRS cells of HL patients, while no expression of these RTKs was observed in normal B cells or B-cell NHL cells (87). This evidence concerns the gene DDR2 and Hodgkins lymphoma.