Dermatofibrosarcoma Protuberans (DFSP)

Figure 5.15 A: DFSP, chest (Courtesy of Dr. Sophie M. Worobec) B: DFSP (Reprint from Markman M, ed. Atlas of Cancer. Philadelphia: Current Medicine Inc; 2002) C: Atypical fibroxanthoma (Reprint from Bolognia JL, Rapini R, Jorrizo JL. Dermatology. 2nd ed. St. Louis, MO: Mosby; 2008)

• Uncommon neoplasm often due to chromosomal abnormality: characteristic reciprocal translocation t(17;22)(q22;q13) resulting in fusion of collagen 1 α 1 and platelet-derived growth factor B (COL1A1-PDGFB), a fusion oncogene; this is the basis for treating such tumors with PDGF inhibitor like imatinib (Gleevec^®)
• Presents as slow-growing large nodule or plaque with multiple protuberances, commonly on trunk (followed by extremities) in middle-aged adults
• Histology: ill-defined dense cellular proliferation of monomorphic spindle-shaped fibroblasts in storiform or cartwheel pattern, cells often with mild-to-moderate atypia; ± may infiltrate subcutaneous fat in fascicular pattern (honeycomb appearance); + CD34 but negative factor XIIIa (allowing differentiation from DF)
• Treatment: Mohs surgery or wide local excision (frequently recurs with latter) ± adjuvant radiotherapy