NBI International Colorectal Endoscopic (NICE) Classification

Narrow-band imaging (NBI) is one of the most frequently used optical digital methods of image-enhanced endoscopy that allows endoscopists to characterize colorectal lesions by enhancing the vessel and surface structure on the lesions [1, 2]. Diagnosis based on the vessel morphological change would be ideal for early detection and accurate diagnosis of colorectal polyps because angiogenesis reflects the growth of tumors critically [3]. In Japan, Sano et al., the initial developer of the NBI system, found the specific differences of vessel morphology on the surface to distinguish each pathological type of colorectal polyps. In normal mucosa or hyperplastic polyp, there are hexagonal thin vessels surrounding crypts which cannot be visualized by magnifying NBI due to lacking resolution power in current system. In adenomatous polyp, these hexagonal vessels uniformly become thicker, and hence they are observable on magnifying NBI, known as meshed capillary (MC) vessels. In harboring cancer, MC vessels are more irregular and dense, which eventually proceed to completely destructed structure of vessels (disruption of thick vessel or avascular) in deep (≥1000 μm) submucosal invasive cancer. He originally reported these vessel patterns for corresponding histology as the Sano classification in 2006, which was validated by several studies [4–7]. Based on the Sano classification, multiple NBI classifications of colorectal lesions with or without optical magnification has been proposed worldwide [8–12]. Although the overall diagnostic performance of these NBI classifications have been shown, the validity of their component criteria has not been established. Therefore, endoscopists around the world needed a universal simple NBI classification available even without magnification for the potential of international use.