Bone & joints

• Metabolic bone disease
• Manifestation of hyperparathyroidism
• Caused by increased osteoclastic activity and fibroblastic proliferation
• The term brown tumor derives from the color, which is caused by the vascularity, hemorrhage and deposits of hemosiderin

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• Plain radiograph: well defined, purely lytic lesions that provoke little reactive bone; the cortex may be thinned and expanded but will not be penetrated (AJR Am J Roentgenol 1993;160:752)
• CT: attenuation values will be in the range of blood and fibrous tissue (Radiol Case Rep 2021;16:2482)
• Angiography (DSA): lesions are usually hypervascular (AJR Am J Roentgenol 1993;160:752)
• MRI: appearance depends on the relative proportion of its components; the lesions, therefore, may be solid, cystic or mixed (Skeletal Radiol 2011;40:205)
  • Solid components are intermediate to low intensity on T1 and T2 weighted images, while the cystic components are hyperintense on T2 weighted images and may have fluid-fluid levels
  • T1 C+ (Gd): there can be enhancement of the solid component and septa
• Nuclear medicine: bone scan often shows intense uptake (AJR Am J Roentgenol 1993;160:752)

Contributed by Nasir Ud Din, M.B.B.S.

• Brown tumors regress when the cause of hyperparathyroidism is removed

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• Spongy brown cystic hemorrhagic lesion

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• Lobular pattern composed of groups and clusters of osteoclast-like multinucleated giant cells
• Vascular fibroblastic stroma
• Hemorrhage and hemosiderin deposits
• Tunneling resorption of adjacent uninvolved bone (J Int Oral Health 2015;7:50)

Contributed by Nasir Ud Din, M.B.B.S.

A 50 year old woman presented with a swelling on the right side of her face that gradually increased in size over last 3 years. It was associated with pain, trismus and inability to open her right eye. She also had history of frequent headaches, abdominal pain and renal stones. Xray revealed a lytic lesion within the right mandible. Incisional biopsy was performed and microscopic examination revealed a lesion (shown above). The most likely diagnosis is

1. Aneurysmal bone cyst
2. Brown tumor of hyperparathyroidism
3. Central giant cell granuloma
4. Cherubism
5. Giant cell tumor

B. Brown tumor of hyperparathyroidism. The photomicrograph shows a lesion composed of bony trabeculae showing resorption along with scattered osteoclast-like giant cells in a vascularized spindled stroma. These microscopic findings with above mentioned clinical and radiological features are characteristic of brown tumor of hyperparathyroidism. Aneurysmal bone cyst affects young adults and shows large blood filled spaces with intervening septae containing fibroblasts and giant cells. Central giant cell granuloma produces radiolucent lesions in children and young women and shows osteoclast-like giant cells near hemorrhagic areas, cellular vascular and fibrous stroma and new bone formation at edge of lesion. Cherubism shows bilateral involvement of mandible and maxilla in young individuals and histology is similar to central giant cell granuloma. Giant cell tumor rarely affects mandible and shows uniform distribution of osteoclast type giant cells among mononuclear cells.

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Reference: Brown tumor of hyperparathyroidism

A 49 year old hypertensive and diabetic man presents with a complaint of right mandibular pain, swelling and intraoral bleeding for a period of 12 months. There was a gradual increase in size and pain. Xray revealed a well defined multilocular lesion within the right mandible. Incisional biopsy was performed and microscopic examination revealed a lesion in the given photomicrograph. What is the most likely underlying etiology?

1. Chronic adrenal insufficiency
2. Chronic liver disease
3. Chronic obstructive pulmonary disease
4. End stage renal disease
5. Ischemic heart disease

D. End stage renal disease. The photomicrograph shows a lesion composed of scattered osteoclast-like giant cells in a vascularized spindled stroma characteristic of brown tumor of hyperparathyroidism. End stage renal disease causes decreased glomerular filtration due to reduced nephron function, which results in decreased synthesis of 1,25 dihydroxyvitamin D3 by the kidney. This leads to decreased absorption of calcium by the gut. Consequently, there is an increased level of serum phosphate. Increased serum phosphate causes serum calcium to be deposited in bone, also leading to a decreased serum calcium. In response to low serum calcium levels, the parathyroid glands secrete increased parathyroid hormone, which results in secondary hyperparathyroidism.

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Reference: Brown tumor of hyperparathyroidism