BACKGROUND: The National Comprehensive Cancer Network (NCCN) guidelines recommend preoperative biopsy for diagnosing dermatofibrosarcoma protuberans (DFSP) but limited data support this approach. We characterized DFSP diagnostic practices and compared clinical outcomes based on technique. METHODS: Data were collected for adult patients who underwent resection for initial DFSP presentation between 2003 and 2021 at 10 international institutions. Patients were categorized by excisional versus preoperative biopsy (incisional, punch, core needle biopsies, or fine needle aspiration), and univariate and multivariable analyses were performed. RESULTS: The cohort included 321 patients, with excisional biopsy performed in 51.4% and preoperative biopsy performed in 48.6% of patients. Biopsy type was stable throughout the study period (p = 0.08). There were no differences in sex, disease presentation, or preoperative imaging. In unadjusted analysis, biopsy varied by practitioner specialty, with general surgeons performing nearly 50% of excisional biopsies. Despite similar planned circumferential margins and anatomic location, preoperative biopsy was associated with higher index R0 rate (60.1% vs. 78.6%), fewer total excisions, and fewer complications (38.2% vs. 25.6%, all p < 0.05). However, adjuvant radiotherapy (11.7% vs. 6.0%) and final R0 rates (91.5% vs. 88.4%) were comparable regardless of technique (p > 0.05). In adjusted analysis, excisional biopsy was associated with extremity tumors (odds ratio [OR] 1.79, confidence interval [CI] 1.21-2.66, p = 0.004), treatment in non-academic settings (OR 2.28, CI 1.10-4.73, p = 0.03), and inversely with preoperative imaging (OR 0.47, CI 0.24-0.93, p = 0.03). CONCLUSION: Preoperative biopsy is associated with margin-negative resection, fewer re-excisions, and reduced complications. Clinical suspicion of DFSP is paramount, and preoperative imaging may critically inform biopsy selection prior to index resection.

• Keywords
• Circumferential margins, Dermatofibrosarcoma protuberans (DFSP), Excisional biopsy, Preoperative biopsy, Unplanned excision,
• MeSH
• Biopsy methods   MeSH
• Dermatofibrosarcoma * pathology   surgery   MeSH
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Skin Neoplasms * pathology   surgery   MeSH
• Follow-Up Studies MeSH
• Prognosis MeSH
• Margins of Excision MeSH
• Retrospective Studies MeSH
• Aged MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Multicenter Study MeSH