It has been shown that usually EEC (type I) carcinomas display microsatellite instability and alterations in the PTEN, K-RAS, PIK3CA, and CTNNB1 (beta-catenin) genes, whereas NEEC are characterized preferentially by mutations of p53, STK15, p16, E-cadherin, and c-erb-B2 genes (8–10). This evidence concerns the gene CTNNB1 and carcinoma.