Combined hepatocellular/cholangiocellular carcinoma with sarcomatoid features: genetic analysis for histogenesis

The histogenesis of sarcomatoid transformation in hepatocellular carcinomas (HCCs) and cholangiocellular carcinomas (CCCs) remains unclear. In the current case, microsatellite loss of heterozygosity (LOH) assay and mutational analysis of the p53 gene with immunohistochemical examination were performed to investigate the histogenesis of each component. The tumor was composed of two parts: one part comprised poorly differentiated HCC (HCC portion), while the other part included undifferentiated, sarcomatoid HCC and CCC (combined portion). LOH at D8S555 was detected in both portions. 1-bp cytosine was deleted at codon 241 of exon 7 of the p53 gene in the combined portion. Immunohistochemically, p53 accumulated in the nuclei of undifferentiated, sarcomatoid HCC and CCC cells, suggesting that the p53 gene mutation might be common in these components. These results support the hypothesis that undifferentiated, sarcomatoid HCC and CCC could be offspring from the original HCC.