Intraosseous Venous Malformation of the Rib With EWSR1-NFATC1 Fusion Mimicking Malignancy: A Pediatric Case Report

BACKGROUND: Intraosseous venous malformations are rare, benign vascular bone lesions that may mimic malignant sarcomas on imaging. OBSERVATIONS: A 14-year-old male presented with fever and cough. Imaging revealed an incidental ossified rib mass with aggressive features. CT-guided biopsy was nondiagnostic, whereas open biopsy demonstrated a vascular lesion positive for CD31, FLI-1, and ERG. Molecular testing identified an EWSR1-NFATC1 fusion. Gross total resection was achieved, followed by prolonged disease-free survival, and the patient resumed full athletic activity 7 months after surgery. CONCLUSIONS: This case highlights the value of open biopsy and molecular testing to prevent misdiagnosis and overtreatment of intraosseous venous malformations.