Carciogenesis of colorectal carcinoma

The majority of colorectal cancers are thought to develop from 'benign' adenomas. Histologically adenomatous polyps smaller than 1cm in diameter rarely contain areas of carcinomatous change, whereas the risk increases to 5%-10% when an adenoma reaches 2 cm in diameter.
- Ras gene mutation is prominant in adenomas.
- Deletion on chromosome 17p in the region containing TP53 gene occur in more than 75% of carcinomas.
-> Mutations of the Ras, TP53 genes and LOH on 5q & 18q accumulate during the transition from a small 'benign' adenoma to carcinoma.