Besides conventional chondrosarcoma, several rare chondrosarcoma subtypes are described, comprising about 15% of all chondrosarcomas. Clear cell chondrosarcoma (CCS) is a low-grade malignant tumour, often recurring after curettage, and showing overall survival of about 85%. Mesenchymal chondrosarcoma (MCS) is a highly malignant tumour occurring in bone and soft tissue of relatively young patients. The tumour shows differentiated cartilage mixed with undifferentiated small round cells. It often metastasises and shows a 5-year overall survival of 55%. Dedifferentiated chondrosarcoma (DDCS) is a tumour containing a high-grade non-cartilaginous sarcoma (DD), and a usually low-grade malignant cartilage-forming tumour (WD). The prognosis is poor. The lack of efficacious treatment of these rare tumours emphasises the need to learn more about their characteristics and to unravel potential targets for therapy. We constructed tissue microarrays (TMAs) with 2mm cores of 45 DDCS (WD and DD), 24 CCS, and 25 MCS, in triplicate. Using immunohistochemistry, we investigated protein expression of estrogen-signaling molecules, growth plate-signaling molecules, and other molecules which might be potential targets for therapy. In addition, we gathered genomic information using Agilent 44K oligo arrays. 30% of the WD components were positive for Cox-2. Almost all others were negative. For Bcl2, 88% of the small cells and 32% of the cartilage in MCS were positive. In CCS, WD, and DD 48%, 4%, and 12% were positive, respectively. We demonstrated the presence of ESR1 and aromatase protein in the majority of tumours in all subtypes. Using array CGH, we observed similar aberrations in the two components of DDCS, with additional aberrations in the DD. Celecoxib treatment is not recommended, as most of the tumours are negative for Cox-2. However, the presence of ESR1 and aromatase support a possible effect of anti-estrogen treatment in all subtypes, and application of Bcl2 inhibitors might chemosensitise MCS.
Ewing sarcoma (ES) is an aggressive sarcoma, and is the second most common bone sarcoma in childhood. Disease specific t(11;22)(~85–90%), t(21;22)(~5–10%), or rarer variant translocations with the involvement of chromosome 22 (~5%) are present. At the gene level, the EWSR1 gene fuses with FLI1, ERG or other ETS transcription factor family members. So far, no ES has been identified with a fusion to transcription factors other than ETS. By using a panel of molecular tools such as multicolor FISH and array-CGH, a ring chromosome containing chromosomes 20 and 22 was identified in four ES cases. Molecular karyotyping showed the translocation and amplification of regions of chromosomes 20q13 and 22q12. Cloning of the breakpoint showed an in-frame fusion between the EWSR1 and NFATc2 genes. The translocation led to the loss of the N-terminal, calcineurin-dependent control region. Consequently, the remaining intact DNA binding domain of NFATc2 is under control of the EWSR1 promoter region permitting oncogenic activation. Intriguingly, in all cases a distinct histological feature was observed.
