Adenocarcinomas of the colon and rectum (colorectal cancer, CRC) are malignant epithelial neoplasms. A polyp is a localized lesion that projects above the surrounding mucosa. Adenomatous polyps (adenomas) are benign neoplasms that arise from colorectal glandular epithelium. In the United States (U.S.), cob- rectal adenoma (CRA) prevalence is approximately 25% by age 50 and rises to around 50% by age 70. The histological hallmarks of a CRA are altered glandular architecture and dysplasia of the epithelium. The great majority of CRCs develop from CRAs in a process called the adenoma-carcinoma sequence. This process may take from years to decades for the earliest CRA to progress to CRC (Leslie, Carey et al. 2002). A CRA progresses to become a CRC when the dysplastic cells invade through the muscularis mucosa. While most CRCs develop from CRAs, fewer than 10% of CRAs ever progress to CRC. Hyperplastic colorectal polyps are histologically distinct from CRAs, occur most frequently in the rectum and sigmoid colon, are not neoplastic and do not progress to CRC. Besides CRAs, the inflammatory bowel diseases, ulcerative colitis (UC) and Crohn's disease of the colon (Crohn's colitis), predispose to CRC.
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