Neoplasia in the colon and rectum and its classification

Dysplasia of the colorectal epithelium is the series of architectural and cytological changes that represent unequivocal neoplastic transformation (Riddell et al., 1983) and is a precancerous lesion. As defined by the World Health Organization (WHO) (Hamilton et al., 2000) only when components of the abnormal epithelium have penetrated through the muscularis mucosae into the submucosa is the lesion considered as invasive adenocarcinoma.