Taking advantage of our previous strategy to analyse TCGA tumour data based on RAC1B percentage spliced-in (PSI) [17], we looked at the association between tumours with high or low RAC1B expression (RAC1Bhigh or RAC1Blow) and the presence or absence of mutations in genes involved in the TGFβ pathway. This evidence concerns the gene TGFB1 and neoplasm.