Molecular genetics of small round cell tumors

The small round cell tumors of children and young adults constitute part of a group of undifferentiated tumors, the precise diagnosis of which is often a challenge for the pathologist because of their uniform morphological appearance. Diagnostic cytogenetic analysis and identification of specific chromosomal abnormalities have been especially useful for the classification of some of these tumors. The cloning of the genes and molecular characterization of the associated genetic anomalies have led to the discovery of the mechanisms involved in their neoplastic transformation and identified a variety of tumor-specific molecular genetic markers. Information has also been provided regarding the histogenetic origin and mechanisms of differentiation in these tumors. This review focuses on the tumor-specific genetic markers, particularly those of clinical relevance, and the recently identified genes and deregulation mechanisms associated with them. The availability of these markers provides auxiliary methods with increasingly improved resolution for primary diagnosis and classification of histologically similar tumors and tools for monitoring patients and identifying potential antineoplastic therapy targets.