Supplementary Material for: Dermatofibrosarcoma Protuberans at the Presumed Injection Site Following CoronaVac COVID-19 Vaccination: A Case Report

Dermatofibrosarcoma protuberans (DFSP) is a rare, slow-growing, locally aggressive cutaneous sarcoma. Trauma and scars have been proposed as potential triggers in a subset of cases. Case presentation: We report a 30-year-old man who developed a progressively enlarging mass in the left deltoid region within several months after receiving two doses of the CoronaVac COVID-19 vaccine administered to the same arm. The lesion was diagnosed as DFSP approximately 19 months after vaccination. Histopathology showed a storiform spindle-cell neoplasm with diffuse CD34 positivity, and fluorescence in situ hybridization demonstrated the COL1A1–PDGFB fusion, consistent with DFSP. The tumor was managed with wide local excision with 2-cm clinical margins; final margins were negative. At 24 months of follow-up after surgery, there was no evidence of local recurrence or metastasis. Conclusions: This case illustrates a temporal association between a new mass at a presumed injection site and DFSP. While causality cannot be inferred from a single case, persistent post-injection nodules should prompt evaluation. The overall benefits of COVID-19 vaccination remain substantial.