Brown tumors in chronic renal failure

Clinical History

A 48-year-old woman with chronic renal failure (CHF) on haemodialysis and history of renal transplantation rejection presented with abdominal and left hip pain for a few months and a high parathyroid hormone (PTH) level.

Imaging Findings

Thoraco-abdominopelvic unenhanced CT was performed, in a patient with asthma and history of previous adverse reaction to intravenous contrast. Several osseous lytic lesions were identified (figures 1 to 3), including the mandible (not shown), vertebral axis (figure 1) and pelvic bones (figures 2 and 3).
Ultrasound guided biopsy of the left iliac lesion was performed. Histology showed "giant-cell tumour". After failure of medical treatment, total parathyroidectomy was performed and a follow-up CT is shown (figure 4).

Discussion

Brown tumours (BT) are not true neoplasms, but rather a form of cystic fibrous osteitis, a reparative process that replaces bone for fibroellastic tissue in a context of intense osteoclastic activity [1]. BT are a manifestation of primary or secondary hyperparathyroidism and usually occur late in the course of the disease [2], being more common among women older than 50 years [3]. Chronic renal failure is a well-established cause of secondary hyperthyroidism, and high levels of PTH are related to hipocalcemia, hyperphosphatemia and calcitriol deficiency seen in CRF patients [4]. BT frequent locations include ribs, clavicles, pelvis, femur and facial bones, the latter particularly in the mandible [5]. Lesions are lytic, well-defined, mono or polyostotic, sometimes accompanied by pain at the site. Subperiosteal bone resorption is also an important finding in patients with hyperparathyroidism [6]. Differential diagnosis depends on the number of lesions and their location(s), and includes mainly fibrous dysplasia, infection, multiple myeloma and metastasis (particularly if polyostotic) and giant cell tumor (particularly if located at meta-epiphyseal regions of long bones). Histologically BT are characterized by the presence of multiple giant cells, intraosseous bleedding and tissue degeneration leading to cystic space formation [7]. Similar pattern can be observed in giant cell tumours, fibrous dysplasia and reparative granuloma, so clinical, analytic and imaging elements are of paramount importance to correctly make the diagnosis. Treatment include medical and surgical options for controlling PTH levels, the latter being commonly reserved for refractory cases. BT lesions usually undergo rapid sclerosis after PTH levels normalize [6].

Take home message:
Multiple lytic lesions in context of high PTH levels should always raise suspiction for BT.

Differential Diagnosis List

Final Diagnosis

Brown Tumors of Hyperparathyroidism

URL:	https://www.eurorad.org/case/14325
DOI:	10.1594/EURORAD/CASE.14325
ISSN:	1563-4086