Ewing sarcoma of the first metacarpal: a rare case report with thumb-sparing resection and fibular graft reconstruction.

Background: Ewing sarcoma is a malignant primary bone tumor that predominantly affects the long bones and pelvis of children and adolescents. Involvement of the hand is exceptionally rare, particularly at the level of the first metacarpal. When the dominant thumb is affected, treatment becomes especially challenging due to the critical functional role of this structure. Case presentation: We report the case of an 11-year-old right-handed boy who presented with a painful swelling of the right thumb. Imaging revealed an aggressive osteolytic lesion of the first metacarpal with soft tissue extension. Histology confirmed Ewing sarcoma. After neoadjuvant chemotherapy according to the EuroEWing 2012 protocol, Thumb-sparing resection was performed, including the trapeziometacarpal and metacarpophalangeal joints. Reconstruction was achieved using a non-vascularized fibular autograft. Despite a poor histological response, surgical margins were tumor-free. Adjuvant chemotherapy and radiotherapy were administered. At one-year follow-up, there was no local recurrence, with satisfactory functional outcome of the dominant hand. Conclusion: Ewing sarcoma of the first metacarpal is exceedingly rare. Limb-sparing surgery with fibular graft reconstruction may represent a valid alternative to amputation in carefully selected pediatric patients, even in cases of limited histological response, provided that oncological principles are respected.