Pathologic and Molecular Features of Perihilar Cholangiocarcinoma Based on U-P Point Division.

ABSTRACT

CONTEXT.­ The Japanese Society of Hepato-Biliary-Pancreatic Surgery guidelines propose a classification scheme that differs from the Union for International Cancer Control (UICC) system, in which the anatomic U-P point is the boundary between intrahepatic cholangiocarcinoma and perihilar cholangiocarcinoma (PCC). OBJECTIVE.­ To investigate whether this classification system improves clinicopathologic and genomic differentiation. DESIGN.­ Fifty-eight PCC cases defined by the UICC system were collected and classified into intrahepatic PCC (IPCC) and extrahepatic PCC (EPCC) categories using U-P point division. They were analyzed by next-generation sequencing using a panel that targeted 425 cancer-related genes. RESULTS.­ The IPCC group exhibited a significant larger tumor size compared with the EPCC group (4.67 ± 2.44 cm versus 2.50 ± 0.91 cm, P = .002). The mutation frequency of KRAS proto-oncogene, GTPase (KRAS) Q61 was also significantly higher in the IPCC group than in the EPCC group (16.7% versus 0.0%, P = .03). There were no statistically significant differences in other pathologic features or genomic characteristics, including tumor mutation burden and microsatellite instability. Significant differences in gene mutation rates, such as phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA; 0.0% versus 15.8%, P = .01) and tumor protein p53 (TP53; 34.5% versus 63.2%, P = .04), were observed between PCC and adjacent biliary tract cancers. CONCLUSIONS.­ This study offers valuable insight into the clinicopathologic and genomic features of PCC. It is proposed that the U-P point division may have limited potential to refine the characterization of PCC regarding these features, and that the UICC classification system can readily demonstrate the molecular specificity of PCC.