Dermatofibrosarcoma protuberans (DFSP)

• First described in 1924 by Darier and Ferrand
• Intermediate-grade malignancy thought to arise from dermis
• Appears clinically as a nodular cutaneous mass that may, with time, develop satellite nodules or even nodal/visceral metastases
• Histologically similar to solitary fibrous histiocytoma, and can be confused with plexiform neurofibroma
  • DFSP distinguished from solitary fibrous histiocytoma by diffuse CD34 positivity, and from plexiform neurofibroma by a complete absence of S100 positivity
• 95% of DFSPs characterized by t(17;22), which fuses PDGF-beta gene to the constitutively active Col1A1 promoter, leading to overproduction of PDGF-beta locally
  • Thought to be primarily responsible for observed phenotype
• Primary treatment is wide surgical excision
• Tyrosine kinase inhibitor imatinib active against PDGF-beta receptor-associated tyrosine kinase; has been shown to be effective adjuvant in recurrent disease
• Can dedifferentiate, most commonly into a high-grade fibrosarcoma; secondary fibrosarcoma arising from DFSP typically does not express CD34
• Pigmented variant known as a Bednar tumor

Reference

Enzinger and Weiss’s Soft Tissue Tumors. 4th ed. Mosby 2001.