Fish analysis of supernumerary ring chromosome in dermatofibrosarcoma protuberans.

We describe the light- and electron microscopic, immunohistochemical, cell culture characteristics and cytogenetic findings of a case of dermatofibrosarcoma protuberans (DFSP). Cytogenetically, the lesion exhibited trisomy 8 and a supernumerary ring chromosome as the only clonal abnormalities found in about 35% of the cells analyzed. FISH-analysis of metaphase chromosomes revealed that the ring chromosome contained chromosome 17 sequences. Hybridization with a chromosome 17 centromere specific probe gave three signals in about 19% of the interphase nuclei suggesting that the ring also had a centromere derived from chromosome 17. These observations add to the evidence that supernumerary ring chromosomes, preferentially derived from chromosome 17, and trisomy 8 are non-random abnormalities in DFSP. Our findings also demonstrate the usefulness of FISH for identifying the origin of marker ring chromosomes.