[Experimental colonic cancers]

An experimental model of colonic cancer can be obtained in rodents by administration of 1-2 Dimethylhydrazine. It produces constant, reproducible lesions, ranging from simple anomalies of secretion to invasive cancers, which are identical to those observed in man. It should be noted that the rats and mice used in these experiments do not present spontaneous colonic tumours. This model has contributed to the substitution of the polyp-cancer sequence by the dysplasia-cancer sequence. All of steps of malignant transformation of the mucosa can be followed by histochemistry of the mucins, by ultrastructural examination of the basement membrane and by labeling of the sub-epithelial connective tissue with hyaluronectin. In man, it is possible to define high risk lesions prior to the appearance of polyps.