Activated Wnt signalling in tumours is caused by increased levels of β-catenin, which can be the result of mutations in APC, β-catenin, AXIN1, AXIN2 or β-TrCP (Kinzler and Vogelstein, 1996; Bienz and Clevers, 2000; Liu et al, 2000; Polakis, 2000; Satoh et al, 2000b; Gerstein et al, 2002; Hajra and Fearon, 2002; Taniguchi et al, 2002; Yokota et al, 2002). The gene discussed is APC; the disease is neoplasm.