Molecular diagnosis of sarcomas: chromosomal translocations in sarcomas.

CONTEXT: Sarcomas are rare, numerous in type, and often difficult to definitively classify. Work in the last 2 decades has revealed that a significant subset of sarcomas are associated with specific chromosomal translocations producing chimeric (fusion) genes that play a role in the sarcomas' biology and are helpful in their differential diagnosis. OBJECTIVE: To briefly review the sarcomas associated with specific translocations presenting Ewing sarcoma and synovial sarcoma as archetypes and to further explain how cytogenetic and molecular biologic approaches are being used in the diagnosis of sarcomas. DATA SOURCES: This work is based on a selected review of the relevant medical and scientific literature and our extensive experience with molecular testing in sarcomas. CONCLUSIONS: In addition to, and complementing, the traditional diagnostic methods of examination of hematoxylin-eosin stained slides, immunohistochemistry, and sound clinical-pathologic correlation, additional cytogenetic and molecular biologic methods are being increasingly utilized and relied on in sarcoma pathology. These methods include chromosomal karyotyping, fluorescence in-situ hybridization, spectral karyotyping, and polymerase chain reaction- based methods for demonstrating specific chromosomal translocations and fusion genes. Understanding the basis of these methods and their application is critical to better provide accurate and validated specific diagnoses of sarcomas.