APC and adenoma: Many of the genetic changes leading to the multi-step progression from adenoma to carcinoma have been described, such as mutations of the adenomatous polyposis coli (APC) gene, K-Ras (Morris et al, 1996), SMAD2, SMAD4 (Thiagalingam et al, 1996), p53 (Nigro et al, 1989), and mismatch repair genes (hMSH2, hMLH1, PMS1, GTBP (Kinzler and Vogelstein, 1996; Perucho, 1996; Chung, 2000).