The differential diagnosis of solid pancreatic masses by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) is currently suboptimal. Needle-based confocal laser endomicroscopy (nCLE) is a novel endoscopic technique, which is compatible with the 19-gauge FNA needle. Under endoscopic ultrasonography (EUS) guidance, nCLE enables real-time in vivo imaging of lesion tissues at cellular and subcellular levels. This study aimed to describe nCLE interpretation criteria for the characterization of pancreatic masses, with histopathological correlation, and to perform the validation of these criteria.