PDGF-BB is a mitogen initially identified as simian sarcoma viral oncogene homolog. It belongs to the PDGF family which includes five members, PDGF-AA, PDGF-BB, PDGF-AB, PDGFCC, and PDGF-DD. PDGF-AA, AB, and BB dimers are processed intracellularly and secreted as active dimers that readily activate PDGF receptors (PDGFRs). PDGF CC and DD are secreted as full-length, latent dimers, and the proteolytic removal of a CUB domain is required for the growth factor domain of PDGF CC or DD to activate the PDGF receptors. PDGF-BB exerts its biological functions through the activation of dimeric receptors made up of two structurally similar protein-tyrosine kinase receptor subunits (αα-, αβ-, or ββ-PDGFR). PDGF has been characterized as a chemoattractant for vascular smooth muscle cells from both sheep and humans and also for canine tracheal myocytes. In cutaneous remodelling, studies ex vivo revealed that PDGF-BB is a mitogen and chemoattractant for dermal fibroblast. Abnormalities of PDGFR/PDGF are thought to contribute to a number of human diseases, and especially malignancy. Autocrine signalling as a consequence of PDGF-B overexpression is clearly implicated in the pathogenesis of dermatofibrosarcoma protruberans (DFSP).