Disseminated tumor cells in the bone marrow – chances and consequences of microscopical detection methods

The detection of disseminated tumor cells (DTCs) in the hematopoetic system is important for various reasons. It is essential for tumor staging. According to the International Neuroblastoma Staging System (INSS) only the cytomorphological examination of bone marrow smears is accepted despite the fact that an infiltrate below 0.1%, can hardly be detected and even infiltrates of more than 10% are sometimes overlooked. Another important aspect is the monitoring of the disease response to cytotoxic drugs by quantifying DTCs. Moreover, bone marrow aspirates represent an ideal source to determine the genetic and biological make up of DTCs at diagnosis and during follow up. Key issues that can be tested on DTCs are: determination of the proliferation capacity, the apoptotic rate, the drug sensitivity etc. The prerequisite for such a bone-marrow diagnosis, however, is the unequivocal identification of disseminated tumor cells. Thus, in order to avoid false positive and false negative results, which are a risk in bone-marrow diagnostics, a system was developed to distinguish tumor cells from non-neoplastic cells and to facilitate the gain of insights into the biological make-up of tumor cells more easily [1,2].