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A Clinicopathologic Review of a Case Series of Dermatofibrosarcoma Protuberans with Fibrosarcomatous Differentiation

Background: Dermatofibrosarcoma protuberans with fibrosarcomatous differentiation (DFSP-FS) is a rare variant of DFSP with a more aggressive clinical course, characterized by higher rates of local recurrence, metastasis, and death. Methods: We conducted a clinicopathologic review of all DFSP-FS cases that occurred in Alberta, Canada, from 1997 to 2007. Results: Of the 75 DFSP cases reviewed, 4 demonstrated fibrosarcomatous differentiation. Three patients were female and one was male, and the age range was 25 to 76 years. Three tumors invaded to skeletal muscle, whereas one invaded to subcutaneous tissue only. Although perineural invasion was noted in all four cases, none exhibited lymphovascular space invasion. One local recurrence developed, and two of four tumors metastasized. Metastasis was associated with tumor size, tumor necrosis, grenz zone involvement, ulceration, thickness, and tumor grade. One patient died within 5 years of diagnosis. Conclusion: DFSP-FS represents a more aggressive subtype of DFSP. Several features of DFSP-FS may impart a higher risk of metastasis.