TP53 and Barrett esophagus: Spatial genetic ITH measured in 164 individual glands that were laser capture-microdissectedfrom 16 samples of eight Barrett’s oesophagus cases. Glands were screened for tumour suppressorgene loss of heterozygosity (LOH) andCDKN2A/TP53 mutations. Marked heterogeneity betweenglands was identified across individual samples, and multiple independent clones were present(bearing no shared founder mutation between the clones). A mosaic pattern of clones across theBarrett’s segment was observed.