RING CHROMOSOMES IN DERMATOFIBROSARCOMA PROTUBERANS ARE COMPOSED OF INTERSPERSED SEQUENCES FROM CHROMOSOME-17 AND CHROMOSOME-22

Ring chromosomes are found in most dermatofibrosarcoma protuberans (DF SPs), and recent reports demonstrate that portions of the DFSP ring ch romosomes derive from chromosome 17. In this study we characterized ri ng chromosomes in three DFSPs using a combined approach of karyotyping , chromosome painting, and comparative genomic hybridization. Chromoso me painting demonstrated that the ring chromosomes in each DFSP were c omposed of discontinuous, interwoven sequences from chromosomes 17 and 22. Amplification of chromosomes 17 and 22 sequences was confirmed in each of these cases by comparative genomic hybridization, and over-re presentation of chromosomes 17 and 22 sequences was also demonstrated by comparative genomic hybridization in 1 of 2 cytogenetically unremar kable DFSPs. We conclude that amplification of chromosomes 17 and 22 s equences, in ring form, is a characteristic aberration in DFSP.