The involvement of fibroblast growth factor receptor signaling pathways in dermatofibroma and dermatofibrosarcoma protuberans.

Fibroblast growth factors (FGFs) and their receptors (FGFRs) control a wide range of biological functions; however, their involvement in the pathogenesis of dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) is currently unknown. In this study, we first confirmed the histological diagnosis by detecting fusion COL1A1-PDGFB transcripts in DFSP, and examined the expression of all FGFRs (FGFR1-4), some of their ligands (FGF1, 2, 9), and forkhead box N1 (FOXN1) as a downstream target of FGFR3 in DF and DFSP by immunohistochemical analysis. Although we failed to detect the expression of FGF1 and FGF9 as specific ligands for FGFR3 in DF, overexpression of FGFR3 and FOXN1 was observed in the epidermal regions of DF, suggesting that the epidermal regions of DF were similar to seborrhoeic keratosis both in terms of histological features and the activation of FGFR3/FOXN1. In addition, strong expression of FGF2 and FGFR4 was observed in the tumor lesions of DF. Expression patterns of FGFR3/FOXN1 and FGF2/FGFR4 in DF were in contrast with those of DFSP. The activation of FGFR signaling pathways may be not only relevant to the pathogenesis of DF, but also very useful in the differential diagnosis of DF and DFSP.