Form-Vessel Classification of Cholangioscopy Findings to Diagnose Biliary Tract Carcinoma's Superficial Spread

We aimed to evaluate a newly developed peroral cholangioscopy (POCS) classification system by comparing classified lesions with histological and genetic findings. We analyzed 30 biopsied specimens from 11 patients with biliary tract cancer (BTC) who underwent POCS. An original classification of POCS findings was made based on the biliary surface's form (F factor, 4 grades) and vessel structure (V-factor, 3 grades). Findings were then compared with those of corresponding biopsy specimens analyzed histologically and by next-generation sequencing to identify somatic mutations. In addition, the histology of postoperative surgical stumps and preoperative POCS findings were compared. Histological malignancy rate in biopsied specimens increased with increasing F- and V-factor scores (F1, 0%; F1, 25%; F3, 50%; F4, 62.5%; p = 0.0015; V1, 0%; V2, 20%; V3, 70%; p < 0.001). Furthermore, we observed a statistically significant increase of the mutant allele frequency of mutated genes with increasing F- and V-factor scores (F factor, p = 0.0050; V-factor, p < 0.001). All surgical stumps were accurately diagnosed using POCS findings. The F-V classification of POCS findings is both histologically and genetically valid and will contribute to the methods of diagnosing the superficial spread of BTC tumors.