Scanning microscopy of colonic mucin during carcinogenesis: is it clinically applicable?

The integrity of the colonic mucin layer has been reported to be altered during carcinogenesis in both humans and rodents. Prior to attempting scanning microscopic techniques on colonic mucosa of patients at high risk to develop colorectal cancer, these procedures were performed on colonic mucosa from rats with chemically induced colon cancers. Substantial technical difficulties in preparation and serious subjectivity in interpretation of the scanning micrographs were encountered. The major technical problem was the unpredictable retention of the mucin layer upon both normal and cancerous mucosae. Visual interpretation of the integrity or disruption of the mucin layer with the scanning electron microscope revealed variable fenestration and fraying of the mucin in both normal and cancerous colons. Our findings suggest that scanning electron microscopy of colonic mucin may not be a reliable screening procedure for (pre)cancerous changes in human colonic mucosae.