CTNNB1 and neoplasm: Favourable-risk tumours without clonal substructure showed no evidence of clonal genomic evolution (i.e. single-clone expansion), acquiring established driver events (e.g. CTNNB1 mutation in MBWNT; PTCH1 mutation in infant MBSHH) [31] and structural chromosomal alterations at initiation, associated with the development of a single, stable, rapidly expanding clone.