[Masked pediatric pathological femoral fracture : Case report of a sarcoma-associated femoral fracture after adequate trauma].

A 9-year-old boy initially presented with a closed metaphyseal transverse fracture of the distal right femur following a fall from a trampoline. Due to the adequate trauma and lack of initial radiological indications for an underlying pathological bone lesion, the fracture was primarily treated with antegrade elastic stable intramedullary nailing (ESIN). Postoperatively, the patient developed persistent pain, progressive soft tissue swelling and highly atypical callus formation accompanied by osteolytic lesions. Following referral to our pediatric trauma center, the radiological diagnostics of the surrounding region raised the suspicion of a telangiectatic osteosarcoma, further complicated by iatrogenic tumor cell seeding along the intramedullary path of the ESIN in the sense of a skip lesion. The diagnosis was confirmed by reference histopathology. Following neoadjuvant chemotherapy according to the EURAMOS/COSS protocol, the iatrogenic tumor cell dissemination necessitated a total femoral en bloc resection and reconstruction using a modular total endoprosthesis.