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Brown Tumor

Summary

Hyperparathyroidism results in disorders of bone and mineral metabolism. Diffuse and focal lesions may arise in multiple bones. On occasion, a patient with undiagnosed hyperparathyroidism presents with a lytic lesion that may be mistaken for a tumor. These lesions are termed "Brown Tumors" due to the presence of old hemorrhage in the lesion.

Clinically, hyperparathyroidism presents as "stones, bones and groans".
Radiologically, hyperparathyroidism presents as diffuse osteopenia as well as circumscribed lucent areas.
Treatment of hyperparathyroidism depends on the etiology of the condition.
Complete Information on this Tumor
Introduction and Definition: 

Hyperparathyroidism results in disorders of bone and mineral metabolism. Diffuse and focal lesions may arise in multiple bones. The skeletal effects include massive bone resorption, bone fractures, and bone pain, as well as diffuse osteopenia, or circumscribed lytic lesions. On occasion, a patient with undiagnosed hyperparathyroidism presents with a lytic lesion that may be mistaken for a tumor. These lesions are termed "Brown Tumors" due to the presence of old hemorrhage in the lesion. Primary hyperparathyroidism is caused by a parathyroid adenoma, hyperplasia or carcinoma and occurs during the third to fifth decade of life.

Secondary hyperparathyroidism is often the result of chronic renal failure. Several factors contribute to hyperparathyroidism of renal failure including increased phosphorus retention causing decreased calcium, bone resistance to PTH, malabsorbtion of calcium in the gut, and inhibition of 1,25(OH)2D production by increased phosphorous.

Incidence and Demographics: 
Lytic lesions are found more often in women than men and have increased incidence with age. Primary hyperparathyroidism with bone disease has become rare in developed countries due to increased use of routine screening laboratory examinations. However, in less developed countries, patients may still present with primary hyperparathyroidism and advanced bone disease.
Symptoms and Presentation: 

Clinically, hyperparathyroidism presents as "stones, bones and groans". The stones refers to recurrent kidney stones. Bones refers to the bone lesions that occur in severe or prolonged cases. Groans is meant to describe the gastrointestinal symptoms of nausea, vomiting, peptic ulcers and pancreatitis as well as the obtundation that occurs with hypercalcemia.

X-Ray Appearance and Advanced Imaging Findings: 
Radiologically, hyperparathyroidism presents as diffuse osteopenia as well as circumscribed lucent areas. Erosion of the tufts of the phalanges is an associated finding and is more pronounced on the radial aspect than the ulnar. Other characteristic areas of resorption include symphysis pubis, distal clavicle, vertebral bodies and lamina dura (bone at base of teeth).The calvaria may have a granular appearance called "salt and pepper" skull. Hyperparathyroidism has patchy increased activity on bone scan.
Laboratory Findings: 
Numerous, depending on cause. Increased parathyroid hormone (PTH) production results in hypercalcemia due to increased calcium absorption in the gut, increased renal tubular resorption, and increased osteoclastic activity. Serum phosphate, alkaline phospheiase and urate are all elevated.
Differential Diagnosis: 
The differential includes giant cell tumors, reparative granulomas and aneurysmal bone cysts
Preferred Biopsy Technique for this Tumor: 
If confirmatory laboratory findings are present, biopsy may not be needed. Biopsy by tru-cut needle is adequate when simple confirmation of the diagnosis is all that is required.
Histopathology findings: 
Microscopically, there is increased resorption of trabeculae in a "tunneling" or "dissecting' pattern. There is an increased number of osteoclasts on the surface of the bone and resorption of pericellular bone by osteocytes. Marrow fibrosis is present next to the trabeculae and woven bone is present. Osteoclastic resorption produces a small hole that becomes confluent with others to create a brown tumor. Brown tumors are rarely seen now in the developed world, but when they do occur they consist of clustered giant cells around minimal bone and fibrous cellular stroma. Brown tumors must be differentiated from giant cell tumors, reparative granulomas and aneurysmal bone cysts.
Treatment Options for this Tumor: 
Treatment of hyperparathyroidism depends on the etiology of the condition. The tumors resolve once the abnormal metabolic condition is controlled. Most patients are treated before orthopedic problems develop. In severe cases, bone fragility may require surgical stabilization. Primary hyperparathyroidism must be treated by surgical removal of the parathyroid neoplasm. Secondary hyperparathyroidism due to chronic renal failure is treated with dialysis, phosphate restriction, and 1,25(OH)2D replacement, or kidney transplantation.
Special and Unusual Features: 
The following is additional material from "Pathological Fractures as the Presenting Symptom of Parathyroid Adenoma: A Report of Three Cases" by Rajesh Rachha DISCUSSION: Primary hyperparathyroidism is a well-recognised entity identified almost more than a century ago by Von Recklinghausen. He and his co-workers coined the term Osteitis fibrosa cystica1. This condition is more common in females. Peak age incidence is between 30 to 50 years and incidence increases with age, though patient aged as young as 14 years was documented. In U.S.A annual incidence is around 0.2% in patients > 60 years1. All the patients in our series are females with florid changes observed in-patient aged 52 years other 2 patients are aged 20 years and 32 years. Disease results from excessive secretion of parathyroid hormone either due to solitary (50-85%) or multiple (10%) adenomas, hyperplasia (10-40%), or rarely due to a carcinoma of a single parathyroid gland. Extensive bony involvement with pathological fractures as a presenting feature due to parathyroid carcinoma has been documented3. In our series of 3 patients all of them were diagnosed to have solitary parathyroid adenoma. Our first patient aged 52 years had coexisting vitamin D deficiency, which explains severe osteomalacia and multiple fractures. Coexistence of vitamin D deficiency in patients with Primary Hyperparathyroidism may put the patient at a significant higher risk of loosing bone mineral density and development of osteoporosis. Two distinct types of bone lesions are described in primary hyperparathyroidism4. The slowly progressive type- leads to cortical thinning and osteoporosis & the rapidly progressive type. Pathological fractures may occur through a cyst or in a weakened long bone. A principal test at present is the ‘Immunoassay’ for PTH 1-84 as it distinguishes the hypercalcaemia of malignancy from that of hyperparathyroidism5. Once the diagnosis of primary hyperparathyroidism has been made by biochemical analysis, the site or sites of adenomatous or hyperplastic parathyroid tissue must be identified6. Some authors advocated ‘Exploratory neck operation’ as most adenomas are localized in the neck7. CT scan and Thallium subtraction scans are useful for detecting parathyroid pathology in normal as well as ectopic locations. USG of neck can be helpful in picking abnormal parathyroid tissue but CT scan and MRI are more sensitive to assess ectopic sites8. In our series of 3 cases, High Resolution Ultrasound Scan (HRUS) of neck helped in localizing the parathyroid adenoma (90% of adenomas are in the neck). Excised parathyroid gland has to be subjected to histopathological examination to confirm and differentiate adenoma, hyperplasia and malignancy. Histopathological examination in all our 3 cases confirmed the diagnosis of parathyroid adenoma. Our experience with fractures in primary hyperparathyroidism revealed that these take longer to heal and are prone to malunion unless splinted internally or externally. Average time taken for fracture union in our series was 12 months. Non-union of fractures is rare and healing proceeds uneventfully after excision of an adenoma. Bone histology returns to normal within 5-6 weeks6. Brown tumours usually resolve with increase in bone density and sclerosis after parathyroid adenectomy. The extensive skeletal involvement due to hyperparathyroidism has rarely been reported. The substantial improvement in bone density, in promotion of fracture healing and in preventing pathological fractures after successful parathyroid adenectomy has been demonstrated in our series of 3 cases. CONCLUSION: In conclusion, a high index of suspicion is necessary to diagnose this unusual presentation of primary hyperparathyroidism. A pathological fracture in young lady with marked osteopenia is highly suggestive. A combination of biochemical tests, including serum levels of calcium, phosphorus, alkaline phosphatase and parathormone assay will help in diagnosing primary hyperparathyroidism in 90% of the cases. All patients with Primary Hyperparathyroidism should have Vitamin D level assessment in order to exclude the coexistance of Vitamin D deficiency with Primary Hyperparathyroidism. High Resolution Ultrasound Scan of neck provides valuable preoperative information in selected cases especially in those undergoing minimally invasive parathyroid surgery. Surgical excision and calcium supplementation along with external or internal splinting of fractures allowed the fractures to heal.
Suggested Reading and Reference: 
Bullough, Peter Orthopaedic Pathology vi ekrn., Times Mirror Interna¬tonal Publishers Limited, London, 1997. Huvos, Andrew. Bone Tumors: Diagnosis. Treatment and Prognosis W.B. Saunders, Co., 1991. Mankin, Henry, Metabolic Bone Disease Instructional Course Lectires 44:3- 29, 1995.
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