Multiple Osteochondromas: Clinicopathological and Genetic Spectrum and Suggestions for Clinical Management

Multiple Osteochondromas is an autosomal dominant disorder characterised by the presence of multiple osteochondromas and a variety of orthopaedic deformities. Two genes causative of Multiple Osteochondromas, Exostosin-1 (EXT1) and Exostosin-2 (EXT2), have been identified, which act as tumour suppressor genes. Osteochondroma can progress towards its malignant counterpart, secondary peripheral chondrosarcoma and therefore adequate follow-up of Multiple Osteochondroma patients is important in order to detect malignant transformation early

A balanced t(5;17) (p15;q22-23) in chondroblastoma: frequency of the re-arrangement and analysis of the candidate genes

<p>Abstract</p> <p>Background</p> <p>Chondroblastoma is a benign cartilaginous tumour of bone that predominantly affects the epiphysis of long bones in young males. No recurrent chromosomal re-arrangements have so far been observed. Methods: We identified an index case with a balanced translocation by Combined Binary Ratio-Fluorescent in situ Hybridisation (COBRA-FISH) karyotyping followed by breakpoint FISH mapping and array-Comparative Genomic Hybridisation (aCGH). Candidate region re-arrangement and candidate gene expression were subsequently investigated by interphase FISH and immunohistochemistry in another 14 cases.</p> <p>Results</p> <p>A balanced t(5;17)(p15;q22-23) was identified. In the index case, interphase FISH showed that the translocation was present only in mononucleated cells and was absent in the characteristic multinucleated giant cells. The t(5;17) translocation was not observed in the other cases studied. The breakpoint in 5p15 occurred close to the steroid reductase 5α1 (<it>SRD5A1</it>) gene. Expression of the protein was found in all cases tested. Similar expression was found for the sex steroid signalling-related molecules oestrogen receptor alpha and aromatase, while androgen receptors were only found in isolated cells in a few cases. The breakpoint in 17q22-23 was upstream of the carbonic anhydrase × (<it>CA10</it>) gene region and possibly involved gene-regulatory elements, which was indicated by the lack of CA10 protein expression in the index case. All other cases showed variable levels of CA10 expression, with low expression in three cases.</p> <p>Conclusion</p> <p>We report a novel t(5;17)(p15;q22-23) translocation in chondroblastoma without involvement of any of the two chromosomal regions in other cases studied. Our results indicate that the characteristic multinucleated giant cells in chondroblastoma do not have the same clonal origin as the mononuclear population, as they do not harbour the same translocation. We therefore hypothesise that they might be either reactive or originate from a distinct neoplastic clone, although the occurrence of two distinct clones is unlikely. Impairment of the <it>CA10 </it>gene might be pathogenetically relevant, as low expression was found in four cases. Diffuse expression of SRD5A1 and sex steroid signalling-related molecules confirms their role in neoplastic chondrogenesis.</p

Genome-wide analysis of Ollier disease: <it>Is it all in the genes?</it>

Abstract Background Ollier disease is a rare, non-hereditary disorder which is characterized by the presence of multiple enchondromas (ECs), benign cartilaginous neoplasms arising within the medulla of the bone, with an asymmetric distribution. The risk of malignant transformation towards central chondrosarcoma (CS) is increased up to 35%. The aetiology of Ollier disease is unknown. Methods We undertook genome-wide copy number and loss of heterozygosity (LOH) analysis using Affymetrix SNP 6.0 array on 37 tumours of 28 Ollier patients in combination with expression array using Illumina BeadArray v3.0 for 7 ECs of 6 patients. Results Non-recurrent EC specific copy number alterations were found at FAM86D, PRKG1 and ANKS1B. LOH with copy number loss of chromosome 6 was found in two ECs from two unrelated Ollier patients. One of these patients also had LOH at chromosome 3. However, no common genomic alterations were found for all ECs. Using an integration approach of SNP and expression array we identified loss as well as down regulation of POU5F1 and gain as well as up regulation of NIPBL. None of these candidate regions were affected in more than two Ollier patients suggesting these changes to be random secondary events in EC development. An increased number of genetic alterations and LOH were found in Ollier CS which mainly involves chromosomes 9p, 6q, 5q and 3p. Conclusions We present the first genome-wide analysis of the largest international series of Ollier ECs and CS reported so far and demonstrate that copy number alterations and LOH are rare and non-recurrent in Ollier ECs while secondary CS are genetically unstable. One could predict that instead small deletions, point mutations or epigenetic mechanisms play a role in the origin of ECs of Ollier disease.</p