In the present case, sequencing of the multiplex RT-PCR amplification product revealed fusion of exon 25 of COL1A1 to exon 2 of PDGFB. To our knowledge, this is the fourth reported case of atrophic DFSP in which the COL1A1-PDGFB fusion gene was detected: Exons 25 [2], 31 [5], and 2 [11] of COL1A1 were previously reported to be involved in the pathogenesis of atrophic DFSP. This evidence concerns the gene COL1A1 and dermatofibrosarcoma protuberans.