Track: Clinical Studies

Topic: Neoplasia,Carcinogensis,Tumor Biology

Abstract:

Dermatofibrosarcoma protuberans (DFSP) is a superficial mesenchymal neoplasm with low metastatic risk; however, the presence of fibrosarcomatous (FS) transformation can portend a more aggressive clinical course. Assessment for FS transformation can be challenging on histology alone, and while this is often accompanied by diminished CD34 expression, this is not seen in all cases. A recent study found PRAME to be among the most upregulated genes in DFSP compared to other soft tissue sarcomas; however, other studies have shown DFSP to be largely devoid of PRAME expression by immunohistochemistry (IHC). Herein, we explored PRAME expression by IHC in DFSP and DFSP-FS. Among 23 DFSP cases studied, 8 were determined to have FS transformation by three pathologists, with expertise spanning dermatopathology and soft tissue pathology. IHC for PRAME and CD34 were performed on representative blocks. All cases (23/23) were strongly positive for CD34. 6 of 8 DFSP-FS cases were positive for PRAME (1+ in 2 cases, and one case each showing 1-2+, focal 2-3+, 3+, and 4+ staining intensity). 2 of 15 conventional DFSPs were positive for PRAME (1+ positivity in one case and 2-3+ positivity in the other). The correlation between PRAME IHC expression and the presence of FS transformation in DFSP was statistically significant (p<0.05, two-tailed Fisher exact test). Although analysis of more cases is needed, this preliminary data suggest that PRAME positivity may be a helpful marker to help differentiate DFSP-FS from classic DFSP, particularly in cases with retained CD34 expression.

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Maria Faraz, MD