Endocrine Abstracts

Introduction: Brown tumour is a rare, benign, tumour-like lesion of bones.The presence of brown tumour is a rare complication of uncontrolled primary, secondary or tertiary hyperparathyroidism.Brown tumours can be solitary or multifocal and are most commonly located in ribs, clavicles, pelvic girdle, extremities and facial bones (maxilla, mandible, and hard palate).A diagnosis of brown tumour in hyperparathyroidism is established by evaluation of serum calcium, phosphorus and parathyroid hormone levels. Very often a histologic diagnosis of a giant cell tumour is made in case of brown tumour.Treatment of these lesions is often directed to the management of the underlying hyperparathyroidism, which frequently results in regression and resolution of the lesion without surgical intervention. However, surgical treatment may be required in refractory cases or in large symptomatic lesions.

Case presentation: A 67-year-old male was referred to an oral surgeon for a right mandible mass and bleeding that was present for approximately one year. The patient’s past medical history was significant for recurrent nephrolithiasis.An incisional biopsy of the mass was performed and histologic examination suggested giant cell granuloma. Despite the histologic diagnosis, the experienced oral surgeon suspected brown tumour in hyperparathyroidism. The patient was referred to an endocrinologist and additional evaluation was performed.A laboratory examination showed hypercalcemia: total calcium level of 2.94 mmol/l (normal range: 2.14 – 2.53), ionized calcium level of 1.61 mmol/l (normal range: 1.18 – 1.32), hypophosphatemia: 0.66 mmol/l (normal range 0.79 – 1.42) and a high PTH level: 44.02 pmol/l (normal range: 1.59 – 7.24).The patient’s renal function was normal and kidney ultrasound revealed mild bilateral nephrocalcinosis without nephrolithiasis. Bone density test revealed osteoporosis.Neck ultrasound revealed an enlarged parathyroid gland and Tc-99 m MIBI SPECT/CT imaging of the neck and mediastinum showed pathological radiopharmacology uptake posterior of the left thyroid lobe compatible with a parathyroid adenoma.The patient underwent left inferior parathyroidectomy and the pathological findings confirmed the diagnosis of parathyroid adenoma.After one-year follow-up, serum calcium, phosphorus and PTH levels were normal. The excision of the remaining exophytic mandible mass was carried out by an oral surgeon due to slow bone healing.

Conclusion: Brown tumour can be the first manifestation of uncontrolled primary hyperparathyroidism, often misdiagnosed as a giant cell tumour. It is an important differential diagnosis in the evaluation of patients with osteolytic bone lesions, with serum calcium, phosphorus and parathyroid hormone measurements being helpful and widely available diagnostic tools.