Cytogenetic analyses of hepatocellular carcinoma by in situ hybridization with a chromosome-specific DNA probe.

Numerical chromosome analysis has been established in solid tumors by using in situ hybridization (ISH) with a chromosome-specific probe. We analyzed human hepatocellular carcinoma (HCC) by ISH for chromosome 17 and investigated the correlation of its copy number with histologic malignancy, proliferative activity, p53 mutation, and DNA ploidy. Chromosome 17 was hybridized with a pericentromere-specific DNA probe directly on the tumor cells isolated from paraffin blocks of 25 surgically resected HCCs. Proliferative activity was measured by Ki-67 immunohistochemistry, p53 mutation was analyzed by p53 immunohistochemistry, and DNA ploidy was estimated by cytofluorometry. Forty-four percent of the 25 HCCs showed numerical abnormality of chromosome 17. Many disomic cases had a less malignant histology, whereas many polysomic cases had a more malignant histology. The Ki-67 positive index of polysomic cases was higher than that of disomic cases. In 22 cases (88.0%), the copy number of chromosome 17 was well matched with DNA ploidy. However, the numerical abnormality of chromosome 17 did not show a significant correlation with p53 mutation. Two of four HCCs that showed histologic heterogeneity were also heterogenous on ploidy pattern and the copy number of chromosome 17. Conversely, there was one case in which only ISH could demonstrate heterogeneity, although the other features exhibited homogeneity. Numerical chromosome abnormalities correlated with the increase of histologic malignancy proliferative activity, and DNA ploidy. Moreover, ISH analysis was useful in assessing the intratumoral heterogeneity in HCC, especially when current methods failed to detect it. Thus, ISH provides information on important biologic features, such as malignant potential and intratumoral heterogeneity, in HCC.