Brown tumor mimicking giant cell tumor in primary hyperparathyroidism: a case report

Differentiating brown tumor due to primary hyperparathyroidism from a giant cell tumor remains a clinical challenge. Misdiagnosis may lead to inappropriate oncologic treatment and unnecessary surgical interventions. We report the case of a 52-year-old Caucasian white woman of Albanian ethnicity with multiple osteolytic bone lesions and a history of repeated orthopedic surgeries over 5 years. Initial histopathology suggested aneurysmal bone cyst and giant cell tumor, while imaging findings were interpreted as metastatic bone disease, and led to chemotherapy and radiotherapy in the absence of a confirmed primary malignancy. The patient was later referred to our Nuclear Medicine Unit, where a repeat bone scintigraphy indicated metabolic bone disease. A full biochemical evaluation revealed severe hypercalcemia and elevated parathyroid hormone. Parathyroid scintigraphy confirmed a hyperfunctioning parathyroid adenoma. Retrospective review of previous pathology reports supported the diagnosis of brown tumor. The patient underwent successful parathyroidectomy. Biochemical parameters normalized within 3 months postoperatively, and no complications such as hypocalcemia were observed. This case illustrates the importance of early consideration of primary hyperparathyroidism in the differential diagnosis of multifocal lytic bone lesions. Accurate diagnosis requires a multidisciplinary approach combining imaging, histopathology, and biochemical evaluation to prevent misdiagnosis and overtreatment.