Cortical Lytic Lesion of the Proximal Tibia in an 8-Year-Old Child: A Pediatric Diagnostic Conundrum

Introduction: Non-ossifying fibroma (NOF) is a common benign fibrous lesion seen in children and adolescents and is usually asymptomatic. It is often found incidentally and most commonly involves the metaphyseal region of long bones. However, when the lesion arises from the cortical bone and presents with pain, it may clinically and radiologically mimic osteoid osteoma, leading to diagnostic confusion. Case Report: An 8-year-old boy presented with severe pain in the right leg for 3 weeks. Radiographs revealed a cortical lytic lesion in the proximal tibial diaphysis, and magnetic resonance imaging findings were suggestive of osteoid osteoma. Due to persistent symptoms and diagnostic uncertainty, surgical curettage and saucerization were performed. Histopathological examination revealed fibrocollagenous tissue composed of spindle-shaped cells arranged in a storiform pattern with scattered osteoclast-type multinucleated giant cells, confirming the diagnosis of NOF. Microbiological culture showed no growth. Conclusion: Painful cortical lesions in children can mimic osteoid osteoma both clinically and radiologically. Histopathological examination is essential for definitive diagnosis in atypical presentations. This case highlights the importance of considering NOF in the differential diagnosis of painful cortical lesions in children.