IDH1 and neuroblastoma: The absence of mutations in ALK and NRAS was of particular interest (Figure 1) because mutations in these genes have been described in neuroblastoma (~9.2%, 0.83% of cases, resp.; Figure 1) and some epigenetically inactivated candidate TSGs (i.e., RASSF1A, FLIP, CASP8, and HIC1) are common to both PCC/PGL and neuroblastoma. IDH1 and IDH2 mutations have been described in gliomas, leukaemia, and other malignancies (Figure 1) and may cause methylation abnormalities by a similar mechanism to that associated with SDH gene subunit mutations [53].