Introduction of a Novel Evaluation Method for the Differential Diagnosis of Truncal Dermatofibrosarcoma Protuberans and Keloids

Background: Differentiating dermatofibrosarcoma protuberans (DFSP) from keloids presents significant clinical challenges, particularly when skin biopsies are contraindicated. This study introduces a novel, non-invasive diagnostic method leveraging the Japan Scar Workshop Scar Scale (JSS) combined with the cosine of the angle (cosθ) to distinguish between these conditions. Methods: We retrospectively analyzed 43 cases using the new evaluation method, JSS×cosθ, designed specifically for this differential diagnosis. This method applies JSS in conjunction with cosθ to assess lesion characteristics non-invasively. Results: The JSS×cosθ scores effectively differentiated between DFSP and keloids. Scores ≥16 were indicative of keloids, whereas scores <16 suggested DFSP, with these findings achieving statistical significance (p<0.001). Conclusions: The JSS×cosθ scoring system provides a reliable, safe diagnostic tool for DFSP and keloids when biopsy is contraindicated, enhancing diagnostic accuracy and facilitating better treatment outcomes. This method promises to significantly impact the specific management of DFSP and keloids.