- Brown tumors represent a reparative cellular process rather than a neoplastic process.
- In chronic renal disease, continual, excessive urinary calcium excretion can lower the serum calcium level and lead to a rise in parathonmone secretion so that skeletal calcium can be mobilized to maintain normal serum calcium levels.
- This mobilization occurs through rapid osteoclastic turnover of bone, a direct effect of
parathormone on bone.
- In localized regions where bone loss is particularly rapid, hemorrhage, reparative granulation tissue,
and active, vascular, proliferating fibrous tissue may replace the normal marrow contents, resulting in a brown tumor.
- Hemosidenin imparts the brown color.
- Brown tumors have a slightly greater frequency in primary hyperparathyroidism than in secondary hyperparathyroidism (3% vs 2%). However, secondary hyperparathyroidism is much more common than primary hypenparathyroidism so that most brown tumors are associated with secondary hyperparathyroidism.
 Imaging Findings
 Plain film
- Well-defined, purely lytic lesions that provoke little reactive bone. The cortex may be thinned and expanded, but will not be penetrated.
- Attenuation values on CT will be in the range of blood and fibrous tissue.
 Bone scan
- Intensely uptake.
Patient #1: Hip pain in a patient with hyperparathyroidism
 See Also
 External Links
- Chew, FS, Huang-Hellinger, F. Brown tumor. Am. J. Roentgenol. 1993 160: 752
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