Comparing the clinicopathological characteristics of combined hepatocellular–cholangiocarcinoma with those of other primary liver cancers by use of the updated World Health Organization classification

Aims Combined hepatocellular–cholangiocarcinoma (cHCC‐CCA) is an uncommon hepatic malignancy with a poor outcome. The 2019 World Health Organization (WHO) classification modified the definition and discarded the subtypes with stem cell features. However, the differences among cHCC‐CCA, hepatocellular carcinoma (HCC), HCC with stem cell/progenitor features (HCCscf) and intrahepatic cholangiocarcinoma (iCCA) remain undetermined. The aim of this study was to investigate the characteristics of cHCC‐CCA in comparison with those of other primary liver cancers by utilising the updated WHO classification. Methods and results We retrospectively analysed 64 cHCC‐CCA patients and 55 HCCscf patients from December 2007 to May 2018. Propensity score matching was conducted to compare these with HCC and iCCA patients. Clinicopathological characteristics, event‐free survival and overall survival were evaluated with multivariate Cox proportional hazard regression. During a median follow‐up of 55.9 months, cHCC‐CCA patients had significantly poorer survival than HCCscf patients, and survival intermediate between that of HCC patients and that of iCCA patients. Hepatitis B virus (HBV) infection and high levels of tumour‐infiltrating lymphocytes (TILs) were associated with favourable survival in cHCC‐CCA patients. In the multivariate analysis, poor hepatic reserve, absence of HBV infection, stage IV disease and low levels of TILs were significant negative prognostic factors in cHCC‐CCA patients. After being pooled with other primary liver cancers, cHCC‐CCA and iCCA resulted in the worse survival. Conclusions cHCC‐CCA patients have survival intermediate between that of HCC patients and iCCA patients, and HBV infection and high levels of TILs predict favourable survival. Our study provides clinical correlations for the new 2019 WHO classification.