Genomic gains ofCOL1A1-PDFGB occur in the histologic evolution of giant cell fibroblastoma into dermatofibrosarcoma protuberans
ABSTRACT Giant cell fibroblastoma (GCF) is a subcutaneous mesenchymal neoplasm characterized by the chromosomal t(17;22), which results in the formation of the fusion gene COL1A1-PDGFB. This same fusion gene is also seen in the supernumerary ring chromosome of dermatofibrosarcoma protuberans (DFSP). Several studies have addressed the molecular genetics of DFSP but molecular cytogenetic characterization of individual areas and cell components in pure GCF and GCF/DFSP hybrids have not been performed. Herein, we studied the frequency and genomic copy number of COL1A1-PDGFB in pure GCF and GCF/DFSP hybrids, and identified the molecular cytogenetic signatures in individual cells in each component. Four pure GCF and nine GCF/DFSP hybrids were studied. All tumors exhibited classical histological features and CD34 expression. COL1A1 and PDGFB rearrangements were evaluated by fluorescence in situ hybridization (FISH) using probes for COL1A1 and PDGFB on paraffin-embedded thin tissue sections. All GCF and GCF/DFSP hybrids showed unbalanced rearrangements of COL1A1-PDGFB at the molecular cytogenetic level. Genomic gains of COL1A1-PDGFB were found predominantly in the DFSP component of GCF/DFSP hybrids but in none of the pure GCF, suggesting that these gains are associated with the histologic evolution of GCF into DFSP. The molecular cytogenetic abnormalities were found not only in the spindle/stellated cells but also in individual nuclei of the multinucleated giant cells, suggesting that these cells may result from the fusion of individual neoplastic cells.
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ABSTRACT: Dermatofibrosarcoma protuberans (DFSP) is characterized by the presence of the t(17;22)(q22;q13) that leads to the fusion of the COL1A1 and PDGFB genes. This translocation can be detected by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) or fluorescence in situ hybridization (FISH) techniques. We have evaluated the usefulness of a dual color dual fusion FISH probe strategy for COL1A1/PDGFB detection in a series of 103 archival DFSPs and compared the obtained results with RT-PCR analyses. FISH and RT-PCR were carried out on paraffin embedded tissue samples. Regarding the RT-PCR approach, all COL1A1 exons and exon 2 of PDGFB were evaluated. Sensitivity, specificity, positive and negative predictive values were assessed considering the histological diagnosis as the gold standard. We also analyzed the relationship between the genetic findings and the clinicopathological variables of the tumors. The COL1A1/PDGFB translocation was detected in 93% of DFSP. Both techniques showed a similar specificity (100%), but FISH was more sensitive than RT-PCR (90% vs. 72%). Regarding, clinicopathological features, a higher percentage of positive cells detected by FISH was significantly associated with the fibrosarcomatous DFSP variant (P < 0.001). Interestingly, all CD34 negative DFSP (n = 5) were positive for COL1A1/PDGFB translocation by both techniques. In conclusion, the majority of DFSP harbor the COL1A1/PDGFB translocation and FISH technique should be recommended as a routine diagnostic tool, especially in cases showing unusual histopathological subtypes and/or immunohistochemical features.Genes Chromosomes and Cancer 07/2011; 50(7):510-7. DOI:10.1002/gcc.20874 · 3.84 Impact Factor
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ABSTRACT: To compare the sensitivity and specificity of fluorescence in situ hybridization (FISH) with reverse transcription polymerase chain reaction (RT-PCR) in the diagnosis of Ewing sarcoma family of tumors (ESFTs) and other small round-cell tumors (SRCTs) in formalin-fixed paraffin-embedded tissue assembled in tissue microarrays (TMAs). The second objective is to confirm the value of molecular methods and immunohistochemical (IHC) assays, to perform a differential diagnosis between ESFTs and SRCTs with similar or overlapping morphology. A total of 560 cases were selected for the present study out the 806 cases collected from the PROgnosis and THerapeutic Targets in the Ewing's Family of TumorS project. Case selection bias included only the cases with enough material to enable the TMA construction, as FISH analysis and the majority of IHC studies were performed in TMAs. Histopathologic, IHC, and molecular assays were carried out. Of the 560 total cases, 411 (73.4%) were considered informative (with results by FISH and/or RT-PCR assays). From the informative cases, 382 (92.9%) were diagnosed as ESFT, 23 cases (5.6%) as non-ESFT but with specific diagnosis for another established entity, and 6 cases (1.5%) as small round cell tumors not otherwise specified. Sensitivity and specificity for the FISH assays was 96.3% and 95.2%, respectively, whereas RT-PCR presented a sensitivity of 97.5% and specificity of 92.9%. In concordant cases, both methods showed a sensitivity and specificity of 99.2% and 100%, respectively. Twenty-nine cases (7.1%) initially interpreted at morphologic level as atypical ESFTs were finally reclassified, with the support of molecular methods and IHC, as either non-ESFT with another specific histologic type or as small round cell tumors not otherwise specified. FISH and RT-PCR are ancillary techniques possessing high sensitivity in the diagnosis of ESFT; nevertheless, FISH is more specific than RT-PCR in the diagnosis of formalin-fixed paraffin-embedded tissue. Both methods in combination displayed the highest sensitivity and specificity. The combination of histopathologic, IHC, and molecular findings is the method of choice for the diagnosis of ESFT, as well as for the differential diagnosis with other SRCTs.Diagnostic molecular pathology: the American journal of surgical pathology, part B 10/2009; 18(4):189-99. DOI:10.1097/PDM.0b013e3181a06f66 · 2.28 Impact Factor
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ABSTRACT: Approximately one third of soft tissue tumors are characterized by chromosomal aberrations, in particular, translocations and amplifications, which appear to be highly specific. The identification of fusion transcripts not only supports the diagnosis, but provides the basis for the development of novel therapeutic strategies aimed at blocking the aberrant activity of chimeric proteins. Molecular biology, and in particular, cytogenetic and qualitative and quantitative polymerase chain reaction technologies, allow with high efficiency and specificity, the determination of specific fusion transcripts resulting from chromosomal translocations, as well as the analysis of gene amplifications. In this review, various molecular techniques that allow the identification of translocations and consequent fusion transcripts generated are discussed in the broad spectrum of soft tissue tumors.International Journal of Molecular Medicine 04/2014; 33(6). DOI:10.3892/ijmm.2014.1726 · 1.88 Impact Factor