MR imaging of brown tumour with fluid-fluid levels: a report of three cases.

Fluid-fluid levels on CT and MR imaging are a typical feature of aneurysmal bone cysts but have also been reported in many other osseous lesions containing haemorrhage. We report fluid-fluid levels in four brown tumour in three patients with primary hyperparathyroidism in which the initial radiological diagnosis was thought to be a bone tumour. To the authors' knowledge, this is the first time that association has been reported in the international literature.