<italic>In vivo</italic> diagnosis of early‐stage gastric cancer found after <italic>Helicobacter pylori</italic> eradication using probe‐based confocal laser endomicroscopy.

Background and Aim: Early‐stage gastric cancer (EGC) found after <italic>Helicobacter pylori</italic> (Hp) eradication often displays non‐tumorous regenerative epithelium and/or maturated tumorous epithelium overlying the cancerous tissue, which may confuse endoscopic and histological diagnosis. Probe‐based confocal laser endomicroscopy (pCLE) enables <italic>in vivo</italic> real‐time optical biopsy. We compared the diagnostic yields for these EGC cases using conventional white light endoscopy (WL), magnifying endoscopy with narrow‐band imaging (ME‐NBI), pCLE, and endoscopic biopsy; we also compared the accuracy of the horizontal extent diagnosis between ME‐NBI and pCLE. Methods: This study enrolled 30 patients with 36 EGC lesions after successful Hp eradication. Diagnostic yields of WL, ME‐NBI, pCLE, and endoscopic biopsy were prospectively compared. Four points of cancerous margins (oral, anal, anterior, and posterior sites) were also prospectively evaluated with M‐NBI and pCLE to determine the horizontal extent of the EGC. Results: Diagnostic yield was significantly higher with pCLE than with WL and endoscopic biopsy (97 <italic>vs</italic> 72%, 97 <italic>vs</italic> 72%, <italic>P </italic>=<italic> </italic>0.0159, 0.0077, respectively), whereas it did not differ from ME‐NBI (88.9%, <italic>P </italic>=<italic> </italic>0.371). Height of non‐tumorous regenerative epithelium or maturated atypical glands was 104.7 ± 34.2 μm in the pCLE‐positive cases, whereas it was 188.3 ± 27.1 μm in a pCLE‐negative case (<italic>P </italic>=<italic> </italic>0.0004). Diagnostic accuracy of the horizontal margin of EGC was significantly higher with pCLE than with ME‐NBI (92 <italic>vs</italic> 70%, <italic>P </italic>=<italic> </italic>0.0159). Conclusion: pCLE may be helpful for the diagnosis of ambiguous ECG found after Hp eradication because it enables real‐time scanning throughout the lesion and detection of subsurface microstructure. [ABSTRACT FROM AUTHOR]