Brown tumor of the fibula: unusual presentation of an uncommon manifestation. Report of a case and review of the literature.

Brown tumors are erosive bony lesions caused by rapid osteoclastic activity and peritrabecular fibrosis due to hyperparathyroidism, resulting in a local destructive phenomenon. Although brown tumors are the most pathognomonic sign of hyperparathyroidism, they are very rarely observed at present as a result of early detection of hypercalcemia and elevated parathyroid hormone levels. The rare appearance of this entity in everyday practice is troublesome for both patients and physicians, because whenever it emerges, diagnosis could be mistaken for a giant cell tumor of the bone. However, clinical, biochemical, and radiologic findings can easily guide the diagnosis if one considers the full continuum of findings and their association with subject's medical history, instead of focusing only on bone lesion. In this report we present a case of brown tumor in the fibula with a short literature review, whose aggressive presentation and unawareness of the skeletal findings of hyperparathyroidism puzzled the caring doctors. This case illustrates the need for continuous vigilance of any physician, regardless of his specialty or his position in medical services structures.