A Comparison of Frozen and Paraffin Sections in Dermatofibrosarcoma Protuberans

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a tumor with a high local reoccurrence rate. Mohs micrographic surgery offers the highest cure rate. However, differentiating minimal residual tumor from normal skin can be difficult during Mohs surgery. OBJECTIVE: To clarify the problem of determining when a tumor-free plane had been achieved during Mohs surgery for a DFSP. METHODS: In two patients with DFSPs, we compared frozen and paraffin-embedded sections extending from tumor to normal skin, using both H&E and CD34 stains. RESULTS: On frozen, but not paraffin-embedded, sections scattered dermal spindle cells were seen in normal skin. CONCLUSIONS: Scattered dermal spindle cells in the dermis of normal skin make it difficult to differentiate minimal residual tumor from normal dermis during Mohs surgery. A biopsy of normal skin can be useful as a control in this setting.