[Precancerous and early stage colorectal carcinoma: clinico-pathological implications]

With regard to the clinical implication and importance of carcinoma prevention, the histogenesis and pathobiology of the precancerous lesions and conditions of the colorectum are described. Polyps, dysplasia (with and without ulcerative colitis), adenomas and polyposis syndromes are defined, and their potential as markers for an increased risk for colorectal cancer is estimated. For the time being, the prevention of colorectal cancer is only possible by interrupting the multistage carcinogenesis in due course, i.e. during the precancerous stages. The exact knowledge of the latter is the rational of the clinical procedures.