Dermatofibrosarcoma protuberans: the diagnosis of high-grade fibrosarcomatous transformation

Objectives Dermatofibrosarcoma protuberans (DFSP) is an intermediate-grade tumour which may undergo fibrosarcomatous transformation to a high-grade sarcoma (DFSP-FST). DFSP-FST requires wide local resection, and therefore, pre-operative identification is important. The aims of this study are to see if DFSP and DFSP-FST can be differentiated based on MRI appearances, and to determine the ability of ultrasound-guided core needle biopsy (US-CNB) to identify DFSP-FST. Materials and methods Retrospective review of patients with a histological diagnosis of DFSP with/without transformation to DFSP-FST. Patient age, gender, lesion location and maximal size were recorded, as were several MRI features. MRI studies were reviewed independently by 2 musculoskeletal radiologists and the assessed features were then compared with final surgical resection histology. Histological results of US-CNB were also compared with final surgical pathology. Results A total of 42 patients were included, 26 males and 16 females with a mean age of 41.3 years (range 3–78 years). The upper limb was involved in 12 cases, the lower limb in 17 and the trunk in 13. Final surgical histological diagnosis was DFSP in 21 (50%) cases and DFSP-FST in 21 (50%) cases. Mean tumour dimension for DFSP was 32 mm and DFSP-FST 68 mm ( p