Targeted therapy for dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a rare, cutaneous tumor characterized by aggressive local invasion. Local recurrence after excision is common, especially when negative margins are not achieved. DFSP frequently exhibits translocation of chromosomes 17 and 22, t(17;22). This rearrangement fuses the collagen type Ialpha1 (COL1A1) gene to the platelet-derived growth factor B-chain (PDGFB) gene. The resultant chimeric gene causes unregulated expression of platelet-derived growth factor leading to abnormal activation of the platelet-derived growth factor receptor (PDGFR) beta tyrosine kinase through an autocrine loop. This is believed to be the critical event in DFSP tumorigenesis. Imatinib mesylate is a potent inhibitor of several protein tyrosine kinases, including the PDGFRs. Clinical evidence suggests that imatinib mesylate is a safe and effective treatment in DFSP, especially in cases of recurrent or metastatic disease. Three phase II, multicenter clinical trials are open to further investigate the role of imatinib mesylate in DFSP.