Occurrence of Factors Influencing Recurrence and/or Metastasis in Dermatofibrosarcoma Protuberans

Introduction: Dermatofibrosarcoma protuberans (DFSP) is a slow growing tumour with limited metastatic potential. However it acquires aggressive attributes as it enlarges or if it recurs following excision. The fibrosarcomatous (FS) variant of DFSP has a higher propensity for local recurrence and distant metastasis.

Aim: To determine the frequency of findings of markers of aggressive disease including FS-DFSP in patients presenting with DFSP.

Methods: A review of histopathology records of patients diagnosed with DFSPs was undertaken. Data retrieved included patients’ demography, tumour site, size, biopsy type, excision margin, CD34 stain result, mitotic count, presence of necrosis and evidence of fibrosarcomatous change. The Pearson’s chi-square was used to determine if there was an association between DFSP subtype and; gender, age and tumour site. Significance was set at below 5%.

Results: 75 histopathological records were found of which 25.3% were recurrent. Majority 57.3% (43/75) were from female patients. All were black Africans. Their average age was 39.7 years and 66.7% were from the trunk with an average size of 8.1 cm (range: 1.5 cm-19.5 cm). Excision was performed for 57.3% (43/75) and resection margin was adequate in 5.7%.

FS-DFSP was reported in 16.0% (12/75) overall and in 27.9% (12/43) of DFSPs which were excised. 75.0% (9/12) of patients who had FS-DFSPs were females. Only 9.7% of classical DFSPs involved limbs whereas 25.0% (3/12) of FS-DFSPs were in extremities. The median age of patients who had FS-DFSPs was 40.5 years (IQR: 34-46) and their average size was 10.4 cm. Mitotic count of 5 and above per 10 high-power fields was reported in 74.9% (9/12) of FS-DFSPs. Gender, age, tumour site and tumour size did not significantly influence occurrence of classical DFSP and FS-DFSP. The difference in mitotic count for DFSP and FS-DFSP was however statistically significant.

Conclusion: Majority of DFSPs are larger than 5 cm at presentation. FS-DFSP variant is common and affects older patients compared to the classical DFSP. Mitotic count above 5 is likely in FS-DFSP as compared to classical DFSP. Adequate tumour resection margin of 2 cm and above is rarely achieved in our setting, especially for FS-DFSP.