Brown tumors (BTs) are expansile osteolytic lesions complicating severe primary hyperparathyroidism (PHPT). Clinical, radiological and histological features of BTs share many similarities with other giant cell-containing lesions of the bone, which can make their diagnosis challenging. We report the case of a 32-year-old man in whom an aggressive osteolytic lesion of the iliac crest was initially diagnosed as a giant cell tumor by biopsy. The patient was scheduled for surgical curettage, with a course of neoadjuvant denosumab. Routine biochemical workup prior to denosumab administration incidentally revealed high serum calcium levels. The patient was diagnosed with PHPT and a parathyroid adenoma was identified. In light of these findings, histological slices of the iliac lesion were reviewed and diagnosis of a BT was confirmed. Follow-up CT-scans performed 2 and 7 months after parathyroidectomy showed regression and re-ossification of the bone lesion. The aim of this case report is to underline the importance of distinguishing BTs from other giant cell-containing lesions of the bone and to highlight the relevance of measuring serum calcium as part of the initial evaluation of osteolytic bone lesions. This can have a major impact on patients’ management and can prevent unnecessary invasive surgical interventions.
- Although rare, brown tumors should always be considered in the differential diagnosis of osteolytic giant cell-containing bone lesions.
- Among giant cell-containing lesions of the bone, the main differential diagnoses of brown tumors are giant cell tumors and aneurysmal bone cysts.
- Clinical, radiological and histological characteristics can be non-discriminating between brown tumors and giant cell tumors. One of the best ways to distinguish these two diagnoses appears to be through biochemical workup.
- Differentiating brown tumors from giant cell tumors and aneurysmal bone cysts is crucial in order to ensure better patient care and prevent unnecessary morbid surgical interventions.