Several studies have highlighted the opportunity of using cfDNA as a source of genetic material not only for molecular study of aggressive lymphomas, especially DLBCL [11,12,27,28,29,30,31,32], but also in HL [14,26,33,34], FL [35,36,37], MCL [38,39], TCL [40,41], or PML [42,43]. The gene discussed is PML; the disease is lymphoma.