Endocrine Abstracts

Introduction

Parathyroid carcinoma (CaPa) is an extremely rare cause of primary hyperparathyroidism. Patients with CaPa usually present severe hypercalcemia with abrupt bone and renal diseases, neurologic manifestations and gastrointestinal symptoms. However, sometimes the presentation is insidious with nonspecific symptoms and mild hypercalcemia. Surgery is the only curative treatment and after surgery close monitoring of calcium levels are necessary due to high risk of severe hypocalcemia by ’hungry bone syndrome’. Progressive disease is common with local recurrence and distant metastases.

Case Report

A 63-year-old woman with nonspecific bone pain for 7 years and progressive serum calcium elevation went to the hospital with an acute back pain without any sings of traumatic injury. Personal and family history was unremarkable. Laboratory investigations showed serum total calcium level of 4.24 mmol/l (NR 2.2–2.5 mmol/l), parathormone levels (PTH) 1387 pg/ml (NR 15–68.3 pg/ml), phosphate 0.51 mmol/l (NR 0.81–1.55 mmol/l), magnesium 0.61 mmol/l (NR 0.66–1.07 mmol/l), 25-hydroxyvitamin D 25 ng/ml (n>29). Ultrasonography of the neck showed a nodular lesion, with 25 mm at the lower pole of the left thyroid lobe with Tc-99m sestamibi scintigraphy confirming increased uptake in the same location. Genetic tests were negative for MEN1 and HRPT2/CDC73. She underwent surgical resection. The histologic examination confirmed the diagnosis of parathyroid carcinoma with capsular invasion and thyroid tissue involvement. Despite the efforts to prevent ’hungry bone syndrome’, a severe hypocalcaemia was observed in the immediate postoperative period indicating the need to prolong medical treatment. Three months after surgery there was evidence of local recurrence and left thyroid lobectomy was completed. New local recurrence was observed two years after, and the patient underwent resection of the lesion. However, a progressive increase in PTH and calcium levels were observed six months after the last surgery, despite imaging investigations not revealing any evidence of residual or metastatic disease. It was decided to keep the patient under surveillance, as the patient is asymptomatic under calcimimetic therapy (cinacalcet 90 mg), with stabilization of the serum total calcium level.

Conclusion

Parathyroid carcinoma is an extremely rare tumour with challenges in diagnosis and treatment that are often difficult. All these are associated with delayed diagnosis, ineffective treatments, and consequently with poor prognosis. In the presence of hypercalcemia and elevated PTH level, parathyroid carcinoma, although a rare condition, should be considered.