Abstract
Mesenchymal chondrosarcomas (MCs) account for 3–10% of primary chondrosarcomas. The cytogenetic literature includes only ten such tumours with karyotypic information and no specific aberrations have been identified. Using a purely molecular genetic approach a HEY1-NCOA2 fusion gene was recently detected in 10 of 15 investigated MCs. The fusion probably arises through intrachromosomal rearrangement of chromosome arm 8 q. We report a new case of MC showing a t(1;5)(q42;q32) as the sole karyotypic aberration. Through FISH and whole transcriptome sequencing analysis we found a novel fusion between the IRF2BP2 gene and the transcription factor CDX1 gene arising from the translocation. The IRF2BP2-CDX1 has not formerly been described in human neoplasia. In our hospital’s archives three more cases of MC were found, and we examined them looking for the supposedly more common HEY1-NCOA2 fusion, finding it in all three tumours but not in the case showing t(1;5) and IRF2BP2-CDX1 gene fusion. This demonstrates that genetic heterogeneity exists in mesenchymal chondrosarcoma.
Highlights
The classification of sarcomas describes over 50 different histological subtypes [1]
The breakpoint position was further narrowed down using fosmid clones with clone G248P81640F4 giving a split signal, mapping the breakpoint to a genomic area between the 39end of the platelet derived growth factor receptor b gene (PDGFRb) and the large intron 1 of caudal type homeobox 1 (CDX1)
This is the first time an IRF2BP2-CDX1 fusion has been detected in human neoplasia
Summary
The classification of sarcomas describes over 50 different histological subtypes [1]. In approximately 20% of them, recurrent balanced translocations leading to formation of fusion genes were identified [2]. Fusion genes provide diagnostic and sometimes prognostic information on the tumours they characterize and knowledge about them could lead to new targeted therapies [3]. Mesenchymal chondrosarcomas (MCs) are rare tumours that account for 3–10% of primary chondrosarcomas [1]. Their typical histological appearance includes a biphasic pattern with areas of round primitive mesenchymal cells interrupted by chondroid elements [4]. Adequate surgery is the gold standard for treatment of localized disease [6] and the role of chemotherapy and radiotherapy remains poorly defined [7,8]
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