Endoscopic diagnosis of early squamous neoplasia of the esophagus with iodine staining: High‐grade intra‐epithelial neoplasia turns pink within a few minutes

Background and Aim:  The ability to detect early squamous neoplasia of the esophagus can be enhanced considerably by iodine staining during endoscopic examination; however, there has been no study on distinguishing high-grade intra-epithelial squamous neoplasia from low-grade dysplasia by endoscopic examination. We assumed that high-grade intra-epithelial neoplasia could be identified as iodine-unstained areas more distinct and reddish than low-grade dysplasia after the brown color of iodine solution has faded, because there is almost no remaining glycogen-containing epithelium in high-grade intra-epithelial neoplasia. Methods:  Seventy-nine patients who were found to have demarcated iodine-unstained areas (0.5 cm to 1.5 cm at widest part, 121 lesions in total) were studied. After a target lesion was found, the lesion was observed for about 3 min and its discoloration was evaluated. If a light-pink part appeared in the iodine-unstained area, the lesion was regarded as being positive for pink color. If no light-pink part was observed in the lesion within 3 min, the lesion was regarded as being negative for pink color. Results:  Thirty-four (87.2%) of the 39 lesions diagnosed as pink-color positive were histologically confirmed to be high-grade intra-epithelial squamous neoplasia or squamous cell carcinoma, whereas only three (3.7%) of the 82 lesions diagnosed as negative for pink color were histologically confirmed to be high-grade intra-epithelial squamous neoplasia (P < 0.0001). Using the pink-color sign as a diagnostic index for high-grade intra-epithelial squamous neoplasia and squamous cell carcinoma, sensitivity was 91.9% and specificity was 94.0%. Conclusion:  By using the pink-color sign for endoscopic diagnosis, accurate diagnosis without endoscopic biopsy for iodine-unstained areas was possible.