Given these striking similarities, we hypothesised that inactivation of the remaining Pten allele contributes to tumour formation in Pb-Cre;Ptenfl/+Arid1afl/fl mice, and studied PTEN immunoreactivity in clinical endpoint Pb-Cre;Ptenfl/+Arid1afl/fl tumour (Supplementary Fig. 4D). This evidence concerns the gene PTEN and neoplasm.