Brown tumors; a possible pitfall in diagnosing metastatic disease.

Brown tumors (BT) are scarcely diagnosed and present a possible diagnostic pitfall in imaging modalities. Imaging modalities and especially positron emission tomography cannot differentiate between brown tumors and metastatic foci and only clinical diagnosis of hyperparathyroidism and histology will support the diagnosis. We describe the histology, clinical expression, significance and the differential diagnosis of BT. We also describe imaging characteristics and imaging techniques for identifying BT. Brown adipose tissue, unrelated to BT may also mimic metastatic disease in imaging modalities.