Comparing clonality between components of combined hepatocellular carcinoma and cholangiocarcinoma by targeted sequencing

Background/Aim: Combined hepatocellular-cholangiocarcinoma (cHCC-CC) is a very rare type of tumor, comprising these two different components in a single mass. Although several studies have determined the genetic characteristics of cHCC-CC, next-generation sequencing (NGS) data for comparing clonality of cHCC-CC are currently unavailable. Materials and Methods: Four cHCC-CC cases were selected and HCC, CC and normal components from each case were separately micro-dissected. DNA and RNA were isolated from each sample and sequenced by Oncomine Comprehensive Panel interrogating 143 cancer genes using the Ion S5 XL sequence platform. Genetic features of HCC and CC from each patient were compared. Results: All cases successfully produced NGS data. Two cases demonstrated different mutations in their HCC and CC components (biclone), while two cases shared the same mutations in the two components (monoclone). Single nucleotide polymorphisms (SNPs) of TP53 (4/4) and phosphatase and tensin homolog (PTEN) (1/4), and gene amplifications of mesenchymal–epithelial transition factor (MET) (1/4), c-MYC (1/4), and cyclin-dependent kinase 6 (CDK6) (1/4) were found in the CC component. In the HCC component, SNPs of TP53 (3/4), PTEN (1/4) and catenin beta 1 (CTNNB1) (1/4) and cyclin D1 (CCND1) amplification (1/4) were detected. Two biclonal cases showed a histologically distinct border between HCC and CC components with or without intermediate cell foci. Two monoclonal cases showed a histologically ambiguous border between HCC and CC components with more intermingled pattern than biclonal cases. Conclusion: Based on our study, cHCC-CC can be genetically divided into biclonal and monoclonal forms. Therefore, separate sequencing of each component of cHCC-CC is recommended for exact molecular classification and targeted therapy.