Chromoendoscopy and magnification endoscopy for diagnosing esophageal cancer and dysplasia.

Based on preliminary reports, the use of chromoendoscopy and magnification endoscopy appears to be a valuable adjunct to standard endoscopy for the detection and classification of metaplastic and dysplastic lesions of the esophagus. Ideally, the use of this technique would enable the endoscopist to rule in or out the presence of intestinal metaplasia and dysplastic/cancerous epithelium by obtaining only a minimal number of targeted biopsy specimens--or potentially taking no biopsies at all, which could transform upper endoscopy into a much more effective screening and surveillance tool. There are several problems with the use of chromoendoscopy and magnification endoscopy in the esophagus. This technique is operator-dependent (ie, dependent on the skill and experience of the endoscopist). Studies reporting the accuracy of chromoendoscopy remain mixed, especially for Barrett's esophagus and dysplasia, which is likely explained by differences in techniques and materials used in the investigations. Staining within the esophagus is often patchy and uneven. Poor spraying technique can exaggerate irregular uptake by the mucosa. There is a high false-positive rate when staining gastric-type epithelium or in the setting of inflammation. Areas of dysplasia or cancer might take up stain in an irregular manner or might not stain at all. Magnification only allows the endoscopist to observe small areas of mucosa at a time, increasing the overall difficulty of the procedure and procedure length. Currently, the greatest body of literature exists concerning the use of Lugol's solution for the diagnosis of squamous cell dysplasia/carcinoma of the esophagus and methylene blue for diagnosing Barrett's esophagus. If used consistently by practicing physicians, the accuracy of biopsies could be improved. If endoscopic ablative therapy for high-grade dysplasia and early carcinoma (eg, photodynamic therapy and endoscopic mucosal resection) becomes accepted, sensitive methods of detecting residual metaplastic or dysplastic epithelium after ablation will be needed to help guide additional endoscopic therapy. Chromoendoscopy and magnification endoscopy could prove helpful in this setting. Further research in this field needs to be performed. As a first step, a uniform classification system for staining and magnification patterns should be devised. Future studies could then be performed using consistent terminologies. More controlled investigations with larger numbers of patients must be performed before tissue staining and magnification endoscopy become a part of day-to-day endoscopic practice. Lugol's chromoendoscopy is a simple technique for the detection of synchronous squamous dysplasia and cancer, but a substantial amount of work remains to be performed for the validation of chromoendoscopy for the detection of Barrett's esophagus and dysplasia. The ultimate aim of chromoendoscopy and magnification endoscopy in the esophagus is to show improved outcomes (ie, early detection of cancer and improved survival). These goals have not yet been realized and will require welldesigned studies in the future.