Ring chromosome 4 as the sole cytogenetic anomaly in a chondroblastoma: a case report and review of the literature

Temporal Chondroblastoma with a Novel Chromosomal Translocation (2;5) (q33;q13)

The case of a 51-year-old man with a large temporal mass is presented. The mass eroded the floor of the middle fossa medially to the sphenoid sinus. A combined approach with neurosurgery and otolaryngology was performed to achieve maximal resection of the mass. Pathology was typical for chondroblastoma: a rare, benign but locally invasive chondroid tumor. Genetic testing revealed a translocation of (2;5) (q33;q13). This is a unique genetic mutation in all chondroid tumors to our knowledge. The diagnostic utility or role of this mutation in the pathobiology of this tumor remains to be determined.

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

Background

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.

Results

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 (SRD5A1) 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 × (CA10) 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.

Conclusion

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 CA10 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.

Benign cartilaginous tumors of bone: from morphology to somatic and germ-line genetics

Benign cartilaginous tumors of bones, intrinsic to their name, are tumors forming cartilaginous matrix with a clinically benign behavior. In this group, we recognize osteochondromas, (en)chondromas, chondroblastomas, and chondromyxoid fibromas. This group includes common tumors, that is, osteochondroma and (en)chondroma as well as rare tumors such as chondroblastoma and chondromyxoid fibroma. Several benign and malignant tumors may mimic benign cartilaginous tumors of bones. We reviewed the main morphologic features and the differential diagnosis is discussed. The genetics of these tumors is intriguing ranging from single gene event (ie, EXT mutation in multiple osteochondromas) to heterogeneous rearrangements with no recurrent involved chromosomal regions such as in chondroblastoma. The main genetic findings are hereby reviewed.

Molecular pathology of chondroid neoplasms: part 1, benign lesions

This two-part review presents an overview of the molecular findings associated with both benign and malignant chondroid neoplasms. This first part presents a brief review of methods in molecular pathology along with a review of the cytogenetic and molecular genetic findings in benign chondroid neoplasms. Clinical aspects of the various lesions are briefly discussed, and each tumor is illustrated with representative radiographic and pathologic images. Malignant chondroid neoplasms will be considered in the second part of this review.

Comparison of allelic losses in chondroblastoma and primary chondrosarcoma of bone and correlation with fluorescence in situ hybridization analysis

Chondroblastoma (CBL) is a benign neoplasm of bone for which the genomic characteristics remain unclear. We compared the status of allelic losses of CBL with that seen in a set of chondrosarcomas (CS) to determine whether differences in their natural history and behavior are also reflected genetically. Eleven cases of CBL and 10 cases of CS of different grades were included. Tumors were subjected to microdissection and polymerase chain reaction using 17 markers located near genes on chromosomes 5, 9, 11, 13, 17, and 19. The selected chromosomes are known to be involved in several mesenchymal neoplasms. Fluorescence in situ hybridization was also performed on tumors displaying allelic losses, with dual-color probes for 9p, 17p, and 13q. Fractional allelic losses per gene ranged from 18.2% to 63.7% in CBLs and from 28.6% to 66.7% in CSs. Loss of heterozygosity (LOH) of 5q, 9p, 11p, 13q, and 19q occurred in both CBLs and CSs. Loss of heterozygosity of 17p (p53 locus) occurred in 7 of 11 CBLs and in only 1 case of recurrent CS. The pattern of allelic loss was similar in low-grade CSs and CBLs. Loci with LOH in both tumor types suggest possible involvement of the genes p53, RB1, CDKN2/p16, ERC, and XRCC in tumorigenesis. Overall correlation between LOH and fluorescence in situ hybridization results was 90% with 17p13, 80% with 9p, and 60% with 13q. The role of p53 in CBL is uncertain; however, given the benign behavior of this tumor, it is probably unrelated to tumor progression.

Monitoring of engraftment and progression of acute lymphoblastic leukemia in individual NOD/SCID mice

OBJECTIVE

The aim of this study was to develop an animal model for human acute lymphoblastic leukemia (ALL) in which the kinetics and characteristics of leukemia can be sequentially monitored in individual mice.

MATERIALS AND METHODS

NOD/SCID mice were inoculated intravenously with primary ALL. Progression of leukemia was monitored throughout the development of disease by determination of absolute leukemic cell counts (LCC) in peripheral blood.

RESULTS

LCC as low as 10(4) leukemic cells/mL blood could be detected. ALL cells from 5 of 5 patients engrafted, and after identification of the first leukemic cells in peripheral blood, LCC increased exponentially. Leukemic cells showed specificity of homing to spleen and bone marrow, and LCC strongly correlated with the level of leukemic engraftment in these organs throughout disease progression, demonstrating that LCC are representative for overall leukemic burden. Cytogenetic analysis of leukemic cells recovered after six successive in vivo transfers revealed no major karyotypic changes as compared to primary cells, and selection of the dominant clones was observed. This selection process was reflected by an increase in the rate of leukemic progression as compared to the first inoculation, demonstrating the accuracy with which kinetics of leukemic progression can be studied by determination of LCC.

CONCLUSIONS

This model is suitable for detailed studies of kinetics and characteristics of ALL in vivo, and it may be useful for monitoring effects of novel therapeutic regimens.

Supernumerary ring chromosomes derived from the long arm of chromosome 12 as the primary cytogenetic anomaly in a rare soft tissue chondroma

Supernumerary ring chromosomes varying with respect to both size and number were found as the primary cytogenetic anomaly in a rare benign soft tissue chondroma resected from the floor of the mouth of a 3-year-old girl. Reverse fluorescence in situ hybridization paint probes prepared by polymerase chain reaction from microdissected rings produced fluorescent signal over two large but discontinuous parts of the chromosome 12 long arm, subdivided into four regions. This case expands the spectrum of mesenchymal neoplasms in which ring chromosomes have been described as the primary genetic anomaly. A review of the literature reporting similar findings in other soft tissue tumors further supports the possibility that low-level amplification of chromosome 12 long-arm regions may contribute to abnormal cellular proliferation in a variety of mesenchymal tumors. Genes implicated in the control of the cell cycle such as sarcoma amplified sequence (SAS), the human homolog of the murine double-minute type 2 gene (MDM-2), proto-oncogenes CHOP/GADD153, GLI, A2MR, cyclin-dependent kinase (CDK4), and the high mobility group (HMGIC) gene implicated in mesenchymal tumorigenesis are all located on the long arm of chromosome 12. Chromosomal abnormalities involving the 12q13-q15 region are associated with a wide range of benign soft tissue tumors and sarcomas.