Abstract
BACKGROUND: Murine double minute 2 (MDM2) is an oncogene that inhibits p53, leading to decreased apoptosis. Sarcomas showing MDM2 amplification are rare among pediatric patients. CASE: A 14-year-old boy presented with pleomorphic sarcoma of the head showing MDM2 amplification without a well-differentiated liposarcoma component. Although chemotherapy was initially performed to reduce the tumor size before surgery, the tumor did not shrink. The patient underwent complete surgical resection. Microscopic examination revealed a positive surgical margin; thus, postoperative proton-beam radiotherapy was performed. 3 years after the therapy, no sign of recurrence was observed. CONCLUSION: Macroscopic surgical resection combined with adjuvant postoperative radiotherapy was effective against MDM2-amplified pleomorphic sarcoma refractory to neoadjuvant chemotherapy in a pediatric patient.