Abstract

Background: Fibrosarcomatous (FS) or malignant fibrous histiocytomatous (MFH) transformation of dermatofibrosarcoma protuberans (DFSP) is a rare, but well known, entity. DFSPs with sarcomatous areas have questionable biological behaviour. Several studies suggest that they have a higher risk for local recurrence and distant metastases than ordinary DFSPs. One recent study described no difference in the behaviour of conventional and transformed DFSP.

Aims: To investigate the biological behaviour of a series of transformed DFSPs.

Methods: Eight transformed DFSPs were analysed clinicopathologically. Follow up ranged from four to 36 years.

Results: The tumours involved the trunk (six cases) and lower extremity (two cases) and measured 3.5–8 cm (median, 4). Sarcomatous change presented de novo in all cases. The type of sarcomatous change was FS (five cases) and MFH (three cases). The estimated proportion of sarcomatous area in the tumour was 25–70% (median, 43.37%). Mitotic counts ranged from nine to 16 mitotic figures/10 high power fields in the FS and MFH areas (median, 12), and from one to three in the DFSP areas. Six patients were treated by wide local excision with histopathologically negative margins and two were treated by simple surgical excision with positive margins. Three patients developed recurrences and one developed metastasis during follow up. Of those treated by wide local excision, one developed recurrence. All tumours expressed CD34 in the DFSP component, but only three in the sarcomatous area.

Conclusions: Although DFSP containing sarcoma may be a more aggressive tumour, its behaviour can be influenced by surgical treatment.