Evidence of an association between 6q13-21 chromosome aberrations and locally aggressive behavior in patients with cartilage tumors.

BACKGROUND: The finding of a cytogenetic-pathologic correlation between complex karyotypes and high grade cartilaginous tumors has been reported. However, few cytogenetic reports exist regarding benign or low grade lesions. A subset of low grade malignant cartilaginous tumors is characterized by locally aggressive behavior but no metastatic potential. Because the histopathologic distinction between benign, borderline, or low grade malignant cartilaginous lesions can be difficult, the finding of additional tumor markers associated with the clinical behavior of borderline cartilaginous lesions could be clinically significant.

METHODS: Four cartilaginous tumors, including an osteochondroma (OC), a chondromyxoid fibroma (CF), an enchondroma (EC), and a dedifferentiated chondrosarcoma (DCS), were cultured and harvested using short term, in situ culture techniques. Chromosome analysis was performed by conventional G-banding and fluorescence in situ hybridization was used to confirm G-banding.

RESULTS: The stemlines of all four tumors showed multiple chromosome anomalies that included aberrations of 6q13-21. The OC showed a t(6;16)(q21;p13.3). The CF showed a complex rearrangement between the chromosome 6 homologues, resulting in an inv(6)(p25q23)t(6;6)(q23;q13). This tumor also showed the clonal evolution of telomeric associations resulting in duplications, deletions, and the formation of a ring 15. The EC showed a der(6)t(6;15)(q13;q11)t(15;22)(q22;q13) stemline and subclones with an unstable iso 17q that subsequently fused to both ends of chromosome 16. The DCS showed a del(6)(q13), r(9), +12 stemline.

CONCLUSIONS: The cytogenetic findings of this study suggest the cytogenetic-pathologic correlation of complex karyotypes found in high grade cartilage tumors may extend to lower grade tumors with complex karyotypes. These findings further suggest that chromosome aberrations in the region of 6q13-21 may be associated with locally aggressive behavior in patients with cartilage tumors.