BACKGROUND: Mapping biopsy (MB) can evaluate superficial ductal spread (SDS) through the histopathological diagnosis of cholangiocarcinoma, enabling the selection of an appropriate surgical procedure. This retrospective study evaluated the efficacy of MB using a novel sheath system in distal cholangiocarcinoma (dCCA) cases. METHODS: A total of 199 cholangiocarcinoma cases underwent preoperative diagnosis. Among them, 40, 21, and 26 cases underwent direct, sheath, and peroral cholangioscopy (POCS) MB, respectively, for dCCA. Each group was compared regarding their technical success rate and the diagnostic accuracy for SDS. RESULTS: Although all cases achieved technical success, the median procedure time of POCS (48-min) tended to be longer than direct (33-min) and sheath MB (30-min) (p overall = .092). Diagnostic specificity and accuracy were significantly higher in the sheath group (95.2%, 95.2%) compared to the direct (71.0%, 70.0%) and POCS (60.9%, 57.7%) MB groups (p overall = .019 and .0094). Multivariate analysis revealed that the sheath MB group was an independent significant factor for the accurate margin diagnosis (OR 0.11
95% CI: 0.01-0.86, p = .0358). CONCLUSIONS: The sheath MB method provided the most accurate histopathological diagnosis of SDS in dCCA. To obtain a larger tissue sample and avoid tumor cell contamination, sheath MB is worth performing to assess the accuracy of the preoperative SDS diagnosis.