[Precancerous colorectal tumors].

Preneoplastic lesions of colorectal carcinoma can be divided in non-serrated and serrated lesions. Non-serrated lesions include conventional adenomas (tubular, tubulovillous and villous) and dysplasias associated with inflammatory bowel disease like flat intraepithelial neoplasia, dysplasia-associated lesions or masses (DALM) and adenoma-like masses (ALM). Conventional adenomas are mostly sporadic, but also found in hereditary adenomatous-polyposis syndromes. Hamartous polyposis syndromes are also associated with colorectal cancer. Serrated lesions include hyperplastic polyps, sessile serrated adenomas and traditional serrated adenomas. Based on these precancerous colorectal lesions different molecular subtypes were identified. Histological subtype, size and grade of dysplasia of polyps are essential for risk assessment of colorectal cancer.