Previous studies have identified 2 clinically significant morphologic subtypes of intrahepatic cholangiocarcinoma (ICC) on the basis of anatomic location and/or histologic appearances. Recognizing that these classification schemes are not always applicable practically, this study aimed to establish a novel classification system based on mucin productivity and immunophenotype and to determine the rationale of this classification by examining the clinicopathologic and genetic characteristics of the 2 subtypes defined by this method. We retrospectively investigated 102 consecutive ICC cases and classified them on the basis of mucin productivity and immunophenotype (S100P, N-cadherin, and NCAM). We found that 42 and 56 cases were classified as type 1 and type 2 ICCs, respectively, and only 4 cases were of indeterminate type. Type 1 ICC, generally characterized by mucin production and diffuse immunoreactivity to S100P, arose less frequently in chronic liver diseases and showed higher levels of serum CEA and CA 19-9 than did type 2 ICC, which generally showed little mucin production and exhibited immunoreactivity to N-cadherin and/or NCAM. Type 1 ICC was characterized by several pathologic features, including higher frequencies of perineural invasion and lymph node metastasis. Although the log-rank test demonstrated that type 1 ICC had significantly worse survival, the multivariate Cox regression analysis showed no prognostic significance of this histologic subtype. Genetic analyses revealed that KRAS mutation was significantly more frequent in type 1 ICC, whereas IDH mutation and FGFR2 translocation were restricted to type 2 ICC. In conclusion, the present classification of ICC based on mucin productivity and immunophenotype identified 2 subtypes with clinicopathologic significance.

In obesity-driven and NASH-driven HCC, metabolic reprogramming mediated by the downregulation of CPT2 enables HCC cells to escape lipotoxicity and promotes hepatocarcinogenesis.

Intrahepatic cholangiocarcinoma (ICC) is an extremely aggressive carcinoma. Useful predictors for the patients’ prognosis after surgery have not been fully established. From the University of Tokyo Hospital pathology archives, we reviewed 107 cases of ICC, 54 cases of perihilar cholangiocarcinoma, and 40 cases of extrahepatic cholangiocarcinoma (ECC); we also investigated the significance of tumor budding in ICC, in comparison with perihilar cholangiocarcinoma and ECC. The tumor-budding frequencies were different by tumor location: 40.2% (43/107) in ICC, 70.4% (38/54) in perihilar cholangiocarcinoma, and 60.0% (24/40) in ECC. Tumor budding in ICC was associated with many pathologic indicators associated with invasion, such as major vascular invasion (P=0.012) and Union for International Cancer Control stage (P=0.007). Univariate and multivariate Cox regression analyses revealed tumor budding as a powerful prognostic factor for both recurrence-free survival (RFS) and overall survival (OS) in ICC by univariate (RFS: hazard ratio [HR]: 2.666; 95% confidence interval [CI]: 1.517-4.683, OS: HR: 4.206; 95% CI: 2.447-7.230) and by multivariate analyses (RFS: HR: 3.038; 95% CI: 1.591-5.973, OS: HR: 4.547, 95% CI: 2.348-8.805). Tumor budding was also a significant prognostic factor of perihilar cholangiocarcinoma, but not of ECC. When ICC was divided into 2 subtypes, type 1 (hilar) and type 2 (peripheral), tumor budding was the strong prognostic factor in type 2 ICC, but not in type 1 ICC, suggesting that some differences in biological behavior exist between type 1 ICC and perihilar cholangiocarcinoma. Tumor budding is prognostically important in ICC, and its pathogenetic role in biliary tract carcinomas might be different by anatomic location.

The aim of this study was to elucidate the clinicopathologic characteristics of hepatocellular carcinoma with reactive ductule-like components (HCC-RD), corresponding to combined hepatocellular-cholangiocarcinoma (CHC) with stem cell features, typical subtype. Retrospective clinicopathologic analysis was performed on HCCs surgically treated at the University of Tokyo Hospital between 1995 and 2013. RD components were defined as neoplastic ductular structures composed of small "stem/progenitor-like" cells. There were 46 HCC-RDs, comprising about 3% of all HCCs. Thirty-eight cases of CHC, classical type (classical CHC), were identified during the study period. When compared with conventional HCC, HCC-RD was characterized by younger patient age (P=0.016), higher frequency of female patients (P<0.001), and higher serum α-fetoprotein levels (P=0.005). Serum carbohydrate antigen 19-9 elevation was also more frequently observed in HCC-RD than in conventional HCC (P=0.002). Histologically, clear cell constituents and interstitial fibrosis were more frequent in HCC-RD than in conventional HCC (P=0.003 and <0.001, respectively). When compared with HCC-RD and conventional HCC, classical CHC was characterized by a poorly differentiated HCC component, frequent vascular invasion, and lymph node metastasis (P<0.05). There was little prognostic difference between HCC-RD and conventional HCC, whereas overall and disease-free survival in classical CHC was significantly worse than in conventional HCC. In conclusion, although HCC-RDs do have some unique clinicopathologic characteristics, they have no prognostic significance, and it is not reasonable to include these tumors in the CHC category.

BAP1 and PBRM1 loss is seen frequently in ICC. ICC with BAP1 loss shares features of small-duct type ICC.