Distinction of Intrahepatic Metastasis from Multicentric Carcinogenesis in Multifocal Hepatocellular Carcinoma Using Molecular Alterations

Patients with hepatocellular carcinoma (HCC) frequently have multiple anatomically distinct tumors. In these patients, multifocal HCC could represent intrahepatic metastases (IM) of a single cancer or multicentric carcinogenesis (MC) with multiple independent neoplasms. In order to determine the frequency and clinical implications of these two possibilities, we performed histological and molecular analysis of 70 anatomically distinct HCCs from 24 patients. We assayed mutations in the TERT promoter region by Sanger sequencing and used next generation sequencing to analyze the entire coding regions of seven well-characterized HCC driver genes - based on shared or discordant mutations in these genes, we classified the HCCs in each patient as IM, MC, or indeterminate. Mutations in the TERT promoter were the most common alteration in our cohort, present in 71% of tumors analyzed. Mutations in the remaining genes occurred in less than 20% of analyzed tumors. We were able to determine the relatedness in 58% of the patients analyzed: MC occurred in 41% of patients, with 33% with exclusively MC and 8% with both MC and IM. IM occurred exclusively in 17% of patients, while the remainder were indeterminate. This study highlights the utility of molecular analyses to determine relatedness in multifocal HCC; however, targeted sequencing can only resolve this distinction in approximately 60% of patients with multifocal HCC.