PDGFB rearrangements, 22q13.1
The PDGFB gene, located at chromosome 22, encodes the human platelet-derived growth factor (PDGF) B chain precursor and is the cellular homologue of the v-sis oncogene.
The reciprocal translocations involving the chromosomal region 17q21.33 harboring the COL1A1 (a.k.a. OI4) gene, and the chromosomal region 22q13.1, harboring the PDGFB (a.k.a PDGF2) gene, t(17;22)(q21.3;q13.1), are characteristic for dermatofibrosarcoma protuberans (DFSP), a highly recurrent, infiltrative skin tumor of intermediate malignancy. The rearrangements are cytogenetically characterized by the presence of supernumerary ring chromosomes containing low-level amplified sequences from chromosomes 17q21-qter and 22q10-q13.1, or unbalanced derivatives of the t(17;22)(q21.3;q13.1) translocation. The rearrangement results in a COL1A1-PDGFB fusion protein which is posttranscriptionally processed to a functional platelet-derived growth factor beta chain (PDGFB) protein, and results in PDFGB mediated autocrine and /or paracrine activation of the plateled-derived growth factor receptor-β (PDGFRB). The accurate diagnosis of DFSP, also called Darier Ferrand tumour or Darier-Hoffmann tumour, is important because of the intermediate malignant nature of the DFSP. Giant Cell fibrosarcoma and Bednar tumours also present this specific cytogenetic feature. The prognosis is usually favourable. These tumours are locally aggressive and highly recurrent, but metastases or tumour-related deaths are extremely rare.
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