[Isolated tumor cells in primary malignant liver tumors]

The failure to reduce the mortality of patients with malignant liver tumors (hepatocellular carcinoma, cholangiocarcinoma) is probably a result of the early dissemination of cancer cells to secondary sites, which is usually missed by conventional diagnostic procedures used for tumor staging. Recent developments in the field of molecular biology enable us to detect tumor cells at a submicroscopic level. Therefore, over the past 10 years, sensitive assays have been developed to detect individual carcinoma cells disseminated to regional lymph nodes or distant organs. In contrast to colorectal and also breast cancer where disseminated tumor cells may be of additional prognostic value, few data exist for hepatocellular carcinomas. Until now, no relevant studies have been reported for cholangiocarcinoma. Alpha-fetoprotein and also albumin mRNA have been used for the detection of circulating micrometastatic tumor foci of hepatocellular carcinoma (HCC); however, the interpretation of the results has been equivocal. If hepatocyte-specific mRNAs are detected in the circulation, it is possible to infer the presence of circulating, presumably malignant, liver cells. The literature about the incidence of "micrometastases" and specificity of different assays for hepatocellular carcinomas varies tremendously. This clearly indicates the need for uniformity in protocols. For hepatocellular carcinoma, mRNA for alpha-fetoprotein and albumin is not a specific marker of circulating micrometastases, but may serve for treatment monitoring. Nevertheless, PCR-based techniques are a powerful tool in the therapeutical monitoring of hepatocellular carcinoma and will find their way into the daily practice of diagnostic histopathologists in the near future.