Concomitant DNA copy number amplification at 17q and 22q in dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a tumor of low or intermediate ma lignant potential with a tendency for recurrence. but low rate of metastasi s. The tumorigenesis of DFSP has recently been shown to be associated with the fusion of the collagen type I alpha 1 (COL1A1) and platelet-derived gro wth factor B-chain (PDGFB) genes, often as a consequence of translocation t (17;22)(q22:q13). Cytogenetically, DFSP is often characterized by supernume rary ring chromosomes containing material from chromosomes 17 and 22. A sub set of DFSPs undergo fibrosarcomatous transformation de novo or upon recurr ence, and contain components indistinguishable from fibrosarcoma (FS-DFSP). The fibrosarcomatous transformation appears to carry an increased risk for recurrence and metastasis. and is considered to represent tumor progressio n. The molecular cytogenetic events contributing to tumor progression are u nknown. We used comparative genomic hybridization to analyze DNA copy numbe r changes in 1 1 cases of typical DFSP and 10 cases of FS-DFSP. All cases i n both groups were found to exhibit a gain or high-level amplification on c hromosome 17q and the majority also on 22q. This finding is in line with pr evious studies, and suggests further that not only the COL1A1/PDGFB fusion gene formation but also the role of DNA copy number gains in the 17q and 22 q regions is crucial per se in the pathogenesis of DFSP. Even though FS-DFS Ps displayed a trend toward increase in the number of DNA copy number chang es, the difference was not statistically significant, which indicates that mechanisms other than copy number changes are important in the transformati on process of DFSP. Copyright (C) 2001 S. Karger AG, Basel.