[Colorectal precancerous conditions from the morphologic viewpoint].

Until their manifestation colorectal cancers pass certain precancerous lesions. This knowledge is extraordinarily significant for prophylaxis of cancer. Among precancerous lesions the different adenomas have the greatest importance. They can occur as solitary or multiple adenomas or adenomatosis coli. Within the so-called cancer-families also the adenomas are considered to be precursors of colorectal cancer. The dignity of neoplasms is determinable by their macroscopic shape and size, by their histological type and the grade of atypia. An exact classification of colorectal adenomas with evaluation of their biological behaviour is a prerequisite for the adequate treatment.