The p53 gene was analysed for mutation in three macro- and micro-scopically different areas of a nodule-in-nodule hepatocellular carcinoma (HCC). Two inner nodules revealed distinct mutations while the surrounding early HCC lesion was negative for mutation. This case clearly demonstrated that the p53 mutation was associated with the progression of HCC from an early to a more advanced stage, and that the primary HCC lesion was composed of genetically heterogeneous subclones. These findings provide direct proof of the involvement of genetic abnormalities in one step of multistage tumor progression.