Hepatocarcinogenesis in non-cirrhotic liver is associated with a reduced number of clonal hepatocellular patches in non-tumorous liver parenchyma

We investigated circumscribed cell proliferations in healthy livers in comparison to non‐cirrhotic livers bearing hepatocellular carcinoma. Using histochemical staining for cytochrome c oxidase, the fourth complex of the respiratory chain, we visualized patch‐forming descendents of regeneratively active liver cells. The clonal nature of these patches was verified by laser‐capture microdissection and Sanger sequencing of the enzyme's core subunits in patches carrying marker mutations on the mtDNA. We demonstrate a highly significant increase of the patch size and also a highly significant increase in the number of patches carrying marker mutations between hepatocellular carcinoma‐free and ‐bearing livers. Thus, the carcinoma‐bearing livers accumulated more genetic damage on mtDNA than the control group. Furthermore, for the first time, we present evidence in hepatocellular carcinoma‐bearing non‐cirrhotic livers of a significantly reduced pool of regeneratively active liver cells that are genetically and functionally altered. The analogy to ageing‐related changes is suggestive of premature ageing of stem cells in non‐cirrhotic hepatocellular carcinoma‐bearing liver as an early step to hepatocarcinogenesis. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.