Abstract: Dermatofibrosarcoma protuberans (DFSP) is a low-grade malignant spindle cell mesenchymal tumor with rare occurrence in children. This study reports a 4-year-old female patient who had recurrent trauma at the same site of the buttock since the age of 1, with repeated hematoma-like masses forming after each injury and healing after dressing changes. One month prior to presentation, a 4 cm×3 cm×1 cm bruise-blue, well-circumscribed hematoma-like mass developed at the identical buttock site following recurrent trauma. The mass ruptured and became infected, with poor wound healing after tumor resection performed at an external hospital. The diagnosis of DFSP was confirmed via pathological consultation and immunohistochemical examination from multiple institutions. Molecular biological testing identified the COL1A1-exon45-PDGFB-exon1 fusion with a variant rate of 9.15%. The patient was treated with wide local excision of the tumor combined with postoperative radiotherapy, and no recurrence was observed during the two-year follow-up period.

Key words: dermatofibrosarcoma protuberans, child, extended resection