Genetics of chondrosarcoma and related tumors.

PURPOSE OF REVIEW

The burgeoning body of information on the genetic changes present in and underlying the development and biology of human cancers has carried implications regarding the possible genetic events that are responsible for not only the genesis of these cancers but also the hope of the cure for these cancers. Chondrosarcomas are a group of tumors that fall into this category. The purpose of this review is to summarize the genetic findings in these tumors.

RECENT FINDINGS

The histopathologic variability of chondrosarcomas is reflected in the complexity and lack of specificity of their cytogenetic and molecular genetic findings, except for extraskeletal myxoid chondrosarcomas. These are characterized in the preponderant number of cases by a translocation, t(9;22)(q22;q12), and in a small number of cases by variant translocations t(9;17)(q22;q11) and t(9;15)(q22;q21). These translocations lead to the formation of abnormal fusion genes and gene products (proteins). In each of these translocations, the CHN gene is involved, resulting in the chimeric fusion genes EWS/CHN, RBP56/CHN, and TCF12/CHN, respectively. The specific translocations and their associated molecular genetic changes are diagnostic of extraskeletal myxoid chondrosarcomas. The abnormal proteins resulting from these fusion genes aberrantly affect gene transcription and cellular signaling pathways thought to be responsible for initiating sarcoma formation. In skeletal (central) chondrosarcomas of varying histopathologic types, the cytogenetic and molecular genetic findings are variable, complex, and apparently lacking in specificity. These changes may reflect a stepwise process (or processes) of oncogenesis involving an array of genes.

SUMMARY

Although some cartilaginous tumors are characterized by specific or recurrent chromosome alterations and molecular genetic changes, much is yet to be learned about the nature and sequence of these genetics events and about their unique role in the stepwise process involved in the development and biology of each tumor type, both malignant and nonmalignant. Until such time, some of the genetic changes, particularly the presence of specific translocations, can be of definite diagnostic value.