Dermatofibrosarcoma protuberans: a clinicopathological, immunohistochemical, genetic (COL1A1-PDGFB), and therapeutic study of low-grade versus high-grade (fibrosarcomatous) tumors.

Dermatofibrosarcoma protuberans (DFSP) is an uncommon cutaneous tumor, usually low grade, except for the fibrosarcomatous variant (DFSP-FS).,We sought to compare the clinicopathological, immunohistochemical, genetic, and therapeutic features between DFSP and DFSP-FS.,The clinicopathological features were reviewed in 63 DFSP and 12 DFSP-FS. Immunohistochemistry and multiplex reverse transcriptase-polymerase chain reaction were carried out using formalin-fixed, paraffin-embedded tissue, using specific primers for collagen type I alpha 1 (COL1A1) and platelet-derived growth factor beta (PDGFB).,DFSP-FS was associated with tumor history longer than 5 years (P = .009), tumor size greater than 4 cm (P = .001), more stages of modified Mohs micrographic surgery (P = .005), expansive subcutaneous infiltration (P = .005), muscular invasion (P = .0001), absence of CD34 staining (P = .018), p53 positivity (P = .006), and increased proliferative activity (P = .004) compared with DFSP. The COL1A1-PDGFB fusion transcript was found in 100% DFSP-FS and 72% DFSP. No association was found between the different COL1A1-PDGFB fusion transcripts and the different histologic subtypes. Wide local excision (2 cm) was performed in 47% of cases and modified Mohs micrographic surgery in 53%. After a mean follow-up of 73 months (range 21-235), 6 patients had local recurrence (5 DFSP, 1 DFSP-FS) and one died of disease (DFSP-FS). The only factor related to local recurrence was the type of surgery (17% wide local excision vs 0% modified Mohs micrographic surgery) (P = .006).,Our study is retrospective. Prospective studies are necessary to confirm our results.,DFSP-FS reflects tumor progression in DFSP, with larger size, particular invasive patterns, p53 expression, and increased proliferative activity. However, as in low-grade DFSP, appropriate surgery permits a tumor-free excision. COL1A1-PDGFB is a useful tool for diagnosis of DFSP and particularly for DFSP-FS.