SAMHD1 and mantle cell lymphoma: Dual staining for CD20 and SAMHD1 in MCL revealed a high variability in the frequency of SAMHD1 positive cells in MCL, and that the intensity of SAMHD1 positivity in MCL nuclei was, with the exception of a few cases, lower than in the lymphoma infiltrating reactive T cells and macrophages (Fig. 1B).