Dermatofibrosarcoma protuberans: clinical, pathological, and genetic (COL1A1-PDGFB ) study with therapeutic implications

Aims:  To analyse the presence of collagen type I alpha 1–platelet-derived growth factor beta ( COL1A1–PDGFB) transcripts in 20 cases of dermatofibrosarcoma protuberans (DFSP) and to assess the relationship between COL1A1 breakpoints and clinical and histopathological variables.
Methods and results:  Multiplex reverse transcriptase-polymerase chain reaction was carried out using frozen tissue. Our series contained 14 men and six women. Histologically, most cases were of conventional type ( n  = 9), followed by fibrosarcoma ( n  = 4), Bednar tumour ( n  = 2), sclerosing ( n  = 2), myoid ( n  = 1) and atrophic ( n  = 1) DFSP, and giant cell fibroblastoma ( n  = 1). Immunohistochemistry revealed CD34 expression in 90% of cases. COL1A1–PDGFB fusion transcripts were present in 89% of cases (exons 18, 19, 20, 25, 26, 31, 33/34, 39, 40, 46, 47 and 48 of COL1A1 with exon 2 of PDGFB) . There was no recurrence of DFSP in any of the 19 patients treated by Mohs surgery. A partial response was obtained in the two patients treated with imatinib.
Conclusions:  The COL1A1–PDGFB fusion was present in all histological subtypes of DFSP, but not all cases expressed the fusion transcript. No association was observed between different COL1A1 breakpoints and clinicopathological parameters. Imatinib mesylate can be useful in locally advanced tumours and metastases.