La dysplasie dans les lesions polypoides et planes du colon

The term polyp applies to any intraluminal projection whatever its nature. Among polyps derived from the epithelium, adenomas are distinguishable by their modified dysplastic epithelium. Three types are recognized: tubular, villous and tubulo-villous. Besides these classical forms, two different lesions have been described more recently: serrated adenomas which share the features of hyperplastic polyps and tubular adenomas that behave as the latter. Flat adenomas cannot strictly be considered as polyps. They are slightly surelevated lesions; histologically they correspond to tubular adenomas. Dysplasia in adenomas can be graded as in any other tissue as mild, moderate and severe or as low and high grade. The severity of dysplasia as well as the cancer risk depend on the size of the adenomas and on their content in villous structures. New techniques complementary to histology such as histochemistry of mucins, immunohistochemistry, demonstration of oncogenes and DNA measurements by flow cytometry or by image analysis can contribute to a better understanding of carcinogenesis; their practical use is nevertheless limited. Pathological analysis of polyps must be performed on correctly oriented specimens to answer the question: has the resection been curative or not? The prognosis and further treatment of the adenomas depends more on the detection of carcinomatous foci than on the degree of dysplasia.SCOPUS: re.j