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.

In conclusion: a new translocation involving EWS and NFATc2 was cloned that is associated with a histological variant of ES. The NFATc2 transcription factor is not a member of the ETS family of transcription factors. NFTAC2 has well characterized functions in T-cell differentiation and immune response. For the first time a direct involvement of NFATc2 in oncogenesis has been shown.

Ollier disease is a rare skeletal disorder. It is characterized by the occurrence of multiple enchondromas with a marked unilateral predominance mainly affecting medulla of the metaphyses and diaphyses of the short and long tubular bones of the limbs, especially the hands and feet. The risk of malignant transformation is suggested to be up to 35%. We hypothesise that Ollier disease is a mosaic condition as it is polyostotic and because of its unilateral predominance. Here we aimed to identify molecular defects in Ollier disease related enchondromas and chondrosarcomas using high resolution single nucleotide polymorphism (SNP) array approach. Affymetrix SNP 6.0 was performed on 67 samples which include 10 blood samples and 3 matched blood-saliva samples as a control; 13 enchondromas and 26 chondrosarcomas of different grades from 30 Ollier patients and normal DNA from 12 Ollier patients for paired comparison.

All samples were divided into three groups: normals, enchondromas and chondrosarcomas. The number of numerical genomic changes in the chromosomes were not different for the enchondromas (p=0.36) while large genomic aberrations were seen in chondrosarcomas as compared to normals (p=0.01). Copy number variation (CNV) analysis showed 95K amplification at 4q13 in 5 out of 13 enchondromas and a 2K deletion at 14q11 in 6 out of 13 enchondromas. Paired loss of heterozygosity (LOH) analysis failed to show LOH in 5 enchondromas at higher resolution. Paired LOH was observed at 3q, 5p, 6p, 6q, 7q, 9p, 12p, 13p and 13q in 7 high grade chondrosarcomas associated with loss of chromosomes.

The results of this study indicate involvement of chromosomes 4 and 14 for the development of enchondromas. We were unable to detect LOH in enchondromas at 1Mb resolution containing approximately 500 SNP probes. High grade chondrosarcomas showed LOH at different chromosomes. In future, we will study LOH and CNV changes at gene level and select candidate genes.