Comprehensive analyses of the clinicopathological features and genomic mutations of combined hepatocellular‐cholangiocarcinoma

Abstract Aim Combined hepatocellular‐cholangiocarcinoma (cHCC‐CCA) is a rare primary liver cancer that has two different tumor phenotypes in a single tumor nodule. The relationship between genetic mutations and clinicopathological features of cHCC‐CCA remains to be elucidated. Methods Whole‐exome sequencing analyses were carried out in 13 primary and 2 recurrent cHCC‐CCAs. The whole‐exome analyses and clinicopathological information were integrated. Results TP53 was the most frequently mutated gene in this cohort, followed by BAP1 , IDH1/2 , and NFE2L2 mutations in multiple cases. All tumors with diameters <3 cm had TP53 mutations. In contrast, six of seven tumors with diameters ≥3 cm did not have TP53 mutations, but all seven tumors had mutations in genes associated with various pathways, including Wnt, RAS/PI3K, and epigenetic modulators. In the signature analysis, the pattern of mutations shown in the TP53 mutation group tended to be more similar to HCC than the TP53 nonmutation group. Mutations in recurrent cHCC‐CCA tumors were frequently identical to those in the primary tumor, suggesting that those tumors originated from identical clones of the primary cHCC‐CCA tumors. Recurrent and co‐occurrent HCC tumors in the same patients with cHCC‐CCA had either common or different mutation patterns from the primary cHCC‐CCA tumors in each case. Conclusions The study suggested that there were two subtypes of cHCC‐CCA, one involving TP53 mutations in the early stage of the carcinogenic process and the other not involving such mutations. The comparison of the variants between primary and recurrent tumors suggested that cHCC‐CCA was derived from an identical clone.