Advantages of magnifying narrow-band imaging for diagnosing colorectal cancer coexisting with sessile serrated adenoma/polyp

Background and Aim: In the present study, we investigated the advantages of narrow-band imaging (NBI) for efficient diagnosis of sessile serrated adenoma/polyp (SSA/P). The main objective of this study was to analyze the characteristic features of cancer coexisting with serrated lesion by carrying out NBI. Methods: We evaluated 264 non-malignant serrated lesions by using three modalities (conventional white light colonoscopy, magnifying chromoendoscopy, and magnifying NBI). Of the evaluated cancer cases with serrated lesions, 37 fulfilled the inclusion criteria. Results: In diagnosing non-malignant SSA/P, an expanded crypt opening (ECO) under magnifying NBI is a useful sign. One hundred and twenty-five lesions (87%) of observed ECO were, at the same time, detected to have type II open pit pattern, which is known to be a valuable indicator when using magnifying chromoendoscopy. ECO had high sensitivity of 80% for identifying SSA/P, with 62% specificity and 83% positive predictive value (PPV). In detecting the cancer with SSA/P, irregular vessels under magnifying NBI were frequently observed with 100% sensitivity and 99% specificity, 86% PPV and 100% negative predictive value. Conclusions: A focus on irregular vessels in serrated lesions might be useful for identification of cancer with SSA/P. This is an advantage of carrying outmagnifying NBI in addition to being used simultaneously with other modalities by switching, and observations can be made by using wash-in water alone. We can carry out advanced examinations for selected lesions with irregular vessels. To confirm cancerous demarcation and invasion depth, a combination of all three aforementioned modalities should be done.