MYCN and neoplasm: Interestingly, group 3/4 medulloblastomas with amplification of MYC or MYCN or duplicated SNCAIP had significantly higher SNV densities at both ECA (Fig. 3i) and MRCA (Fig. 3j) than the remaining tumours, suggesting that later onset of (pre-)malignancy may predispose to the subsequent acquisition of these drivers.