Brown's Tumor Presenting as a Pathological Humerus Fracture: A Rare Diagnostic Pitfall.

Introduction: Brown's tumor represents a late skeletal manifestation of long-standing hyperparathyroidism and is characterized by focal osteoclastic activity. Although benign, its presentation can resemble aggressive bone lesions and may lead to diagnostic confusion, particularly when associated with pathological fractures. Case Report: A 31-year-old male presented with right arm pain and deformity following trivial trauma. Imaging revealed an expansile osteolytic lesion in the humeral shaft with an associated fracture. Biochemical evaluation revealed marked hypercalcemia and significantly elevated parathyroid hormone levels. Functional imaging localized a hyperfunctioning parathyroid lesion. Following metabolic correction, the patient underwent parathyroidectomy and intramedullary fixation of the humerus. Histological findings confirmed parathyroid adenoma and reactive osteoclastic bone changes consistent with Brown's tumor. Conclusion: Metabolic bone disorders such as Brown's tumor should be considered when evaluating lytic lesions with fractures. Early biochemical evaluation is essential to avoid misdiagnosis and unnecessary aggressive surgical intervention.