Reciprocal translocations involving t(17;22)(q21.3;q13.1) are characteristic for dermatofibrosarcoma protuberans (DFSP). DFSP is 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 frequently results in formation of a COL1A1-PDGFB fusion protein which is post-transcriptionally 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 is important because of the intermediate malignant nature of the DFSP and can be facilitated by Fluorescence in situ Hybridization (FISH) analyses.