Contribution of cytogenetics to the management of poorly differentiated sarcomas.

Sarcomas constitute a heterogeneous group of rare tumors that in recent years have been shown by cytogenetic analysis to have a remarkably high incidence of specific and primary alterations. These genetic alterations not only have guided molecular studies in establishing the underlying genes involved, thereby yielding important pathogenetic information, but have also provided clinicians with a valuable tool to add to their diagnostic armamentarium. The addition of molecular cytogenetic (fluorescence in situ hybridization [FISH]) and molecular approaches (reverse transcriptase-polymerase chain reaction [RT-PCR]) has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal imbalances and/or structural rearrangements in sarcomas, including assessment in formalin-fixed, paraffin-embedded tissues. Poorly differentiated sarcomas represent a significant challenge to the pathologist as these neoplasms lack an identifiable hematoxylin and eosin-stained phenotype and often have lost diagnostic immunohistochemical or ultrastructural features as well. In contrast, primary cytogenetic changes and associated molecular events such as the 11;22 translocation in Ewing sarcoma are retained as a given tumor metastasizes or becomes less differentiated, as their presence appears to be vital for sustaining neoplastic transformation. Consequently, demonstration of characteristic, tumor-specific chromosomal aberrations is especially useful in the management of poorly differentiated sarcomas.