Spectral karyotyping reveals 17;22 fusions in a cytogenetically atypical dermatofibrosarcoma protuberans with a large marker chromosome as a sole abnormality

The presence of an extra ring chromosome containing material from 17q and 2 2q, or, less frequently, a t(17;22)(q22;q13), is a cytogenetic hallmark of dermatofibrosarcoma protuberans (DFSP). However, occasionally tumors with o ther, atypical karyotypes are encountered. We describe a case of recurrent DFSP without a ring chromosome or a t(17;22) on standard cytogenetic analys is. In all cells analyzed by G-banding, an additional, large marker chromos ome was present as a sole abnormality. This chromosome apparently included chromosome 8 or the 8q arm, but the origin of its remaining part could not be determined with certainty. To characterize further the abnormal chromoso me, we applied spectral karyotyping (SKY). SKY confirmed the presence of an extra chromosome 8 or arm 8q in the marker and showed that its remaining p art was composed of segments from chromosomes 7, 17, 21, and 22, with two c opies of a 17;22 fusion, Our results and the literature data suggest that, in addition to a specific 17;22 fusion, amplification of material from chro mosomes 17, 22, 8, 5, 7, and 21 may play a role in DFSP development and/or progression. Furthermore, our case demonstrates the usefulness of SKY in de tection of a diagnostically relevant 17;22 fusion in DFSP patients who have unusual karyotypic features. (C) 2001 Wiley-Liss, Inc.