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Early events in human colorectal carcinogenesis. Aberrant crypts and microadenoma.

Experimental studies have allowed the identification of foci of aberrant crypts on the fixed methylene-blue-stained mucosal surface of rodent colons after colon carcinogens administration. Similar lesions can also be observed and quantified on the mucosal surface of the human colon, using the same technique. Several foci showed dysplasia at histological examination, thus allowing the identification of microadenomas. Microadenoma may thus be a precursor lesion of adenomas and colorectal cancer. The identification of aberrant crypt foci and microadenomas in vivo could provide a new end-point for studies on the effect of environmental and genetic factors in the early stages of cancer of the large intestine. Further studies are needed to define the natural history of these lesions. Moreover, a critical evaluation of current colon cancer prevention strategies should be considered.