CHEK2 and neoplasm: In order to evaluate the activation of the DDR machinery in the same set of samples, we investigated the immunostaining for pS1981_ATM, the activated form of a key upstream regulator that controls most DDR events; the staining for pT68_Chk2, a central mediator of DDR that resulted barely detectable in IGCNU and in primary tumours was also analysed (Figure 4).