Significance of a white opaque substance under magnifying narrow-band imaging colonoscopy for the diagnosis of colorectal epithelial neoplasms

Background and AimsThe aim of this study was to examine the significance of a white opaque substance (WOS) found on magnifying narrow-band imaging (M-NBI) for the diagnosis of colorectal neoplastic lesions.MethodsWe retrospectively reviewed colonoscopy records from 2006 to 2012 at our institution and identified cases of endoscopically or surgically resected colorectal epithelial neoplasms observed by M-NBI colonoscopy. The colonoscopic and histologic characteristics of the lesions were compared between WOS-positive and WOS-negative lesions. We further classified the WOS as regular or irregular and compared the histologic characteristics between the two types of lesions.ResultsThere were 105 WOS-positive lesions and 451 WOS-negative lesions. The former were subdivided into lesions with regular and irregular WOS. The incidence of high-grade dysplasia or carcinoma was significantly higher in WOS-positive lesions (61.9%) than in WOS-negative lesions (28.6%) (P < .05). Among the WOS-positive lesions, massive submucosal invasion was more frequent in lesions with irregular WOS (82.4%) than in those with regular WOS (1.4%) (P < .05). Among cancers with massive submucosal invasion, lymph node metastasis was more frequent in cancers with irregular WOS (17.4%) than in those with regular WOS or without the WOS (0%) (P < .05).ConclusionsA WOS in colorectal neoplasms may be an optical marker for high-grade dysplasia and cancer. An irregular WOS may be indicative of massive submucosal invasion and lymph node metastasis.