Post written by Toyoki Kudo, MD, PhD, from the Digestive Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.

We aimed to reveal which endocytoscopic findings may be used as indicators of low-grade adenoma and to assess whether a “resect and discard” strategy using endocytoscopy is feasible. A normal pit-like structure in endocytoscopic images was considered a normal pit (NP) sign and used as an indicator of low-grade adenoma. The primary outcome was the diagnostic accuracy of the NP sign for low-grade adenoma. We evaluated agreement rates between endocytoscopy and pathological diagnosis for surveillance colonoscopy interval recommendation (SCIR) and performed a validation study to verify the agreement rates.

For 748 lesions in 573 cases were diagnosed as colorectal adenoma using endocytoscopy. The results were: sensitivity of the NP sign for low-grade adenoma, 85.0%; specificity, 90.7%; positive predictive value, 96.6%; negative predictive value, 66.1%; accuracy, 86.4%; and positive likelihood ratio, 9.2 (P < 0.001). The agreement rate between endocytoscopy and pathological diagnosis for SCIR was 94.3% (95% confidence interval [CI], 92.2%–96.1%; P < 0.001) under United States guidelines and 96.3% (95% CI, 94.5%–97.7%; P < 0.001) under European Union guidelines. All inter- and intraobserver agreement rates for expert and nonexpert endoscopists had k-values ³ 0.8 except one non-expert pair.

“Resect and discard” strategy markedly decreases the time, labor, and costs required to obtain a pathological diagnosis. In addition, the ASGE proposed this strategy is acceptable in patients with lesions measuring < 5 mm, if precise differential diagnosis of neoplastic and non-neoplastic lesions and patients’ prognoses according to the SCIR can be performed as for conventional pathological diagnosis. However, it is important to note that evidence supporting the 5-mm limit in previous studies was based primarily on a non-magnifying NBI diagnosis, which resulted in frequent poor diagnostic accuracy and limited adoption of the “resect and discard” strategy. If we can precisely and accurately diagnose the target lesions of colorectal low-grade adenoma and avoid discarding invasive cancer and advanced lesions, then the “resect and discard” strategy may become more popular. Therefore, we focused on lesions diagnosed as colorectal adenoma and, of these, only low-grade adenoma, using endocytoscopy.

To the best of our knowledge, our study is the first to validate using endocytoscopy in the differential diagnosis of colorectal adenoma, and our findings indicated that endocytoscopy was highly-accurate for diagnosing low-grade adenoma. Of note, the NP sign proposed in this study effectively differentiated low-grade adenoma, regardless of the lesion size. Furthermore, invasive cancer was distinguished without exception, and our endocytoscopic diagnosis method was also feasible and highly accurate, regardless of an endoscopist’s years of experience performing colonoscopy. The significance of our results relates to the possible implementation of the “resect and discard” strategy, and the possibility of endocytoscopy becoming a beneficial modality using this strategy.

Figure 1. Endocytoscopic images showing neoplastic lesions. A, Endocytoscopic image showing a slit-like lumen, which is a good indicator of adenoma. B, Endocytoscopic image showing the mixed findings of the normal pit-like structure (white arrow) and the slit-like lumen. This mixed finding is considered a positive normal pit sign and an indicator of low-grade adenoma.

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