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Challenges in the management of a rapidly growing dedifferentiated parathyroid carcinoma

Anastasia D Dede¹, Kate Newbold², Khin Thway³, Daniel Morganstein^{1, 2}

¹Endocrinology Department, Chelsea and Westminster Hospital, ²Thyroid Unit, The Royal Marsden Hospital, ³Department of Histopathology, The Royal Marsden Hospital

Introduction: Parathyroid carcinoma is a rare cause of primary hyperparathyroidism, with a reported incidence of 2 cases per 10,000,000 person-years ^[1]. Treatment strategies include surgical resection and management of hypercalcemia. Chemotherapeutic agents have largely proved inefficient and there is lack of trials as the tumour is rare.

Case presentation: A 50-year old lady was referred for further management of a previously resected parathyroid carcinoma. She had been admitted to her local hospital in August 2015 with symptoms of hypercalcaemia. Adjusted serum calcium on admission was 3.28 mmol/l and PTH 31.3 pmol/l. Past medical history was unremarkable and her only medication was omeprazole. She had no family history of hyperparathyroidism. Localisation studies were negative. She underwent neck exploration 4 months later and had parathyroidectomy and right thyroid lobectomy. A right 38 mm parathyroid lesion was resected and the pathology report showed features of a parathyroid “atypical adenoma”. Calcium and PTH levels normalised post-operatively. 3-4 months after her operation she noticed a lump on the right side of her neck. She underwent extensive neck surgery in June 2016 to remove a recurrent tumour. Calcium pre-operatively was normal. The pathology showed a poorly differentiated malignant tumour.

At presentation, post her second surgery, calcium was normal. Imaging did not show any evidence of local recurrence or distant metastases. Pathology from both surgeries was reviewed and it was concluded that the first tumour had areas of poor differentiation and the second tumour was dedifferentiated parathyroid carcinoma. Genetic testing for CDC73 was negative. She was referred for post-operative radiotherapy to the right neck in November 2016. In August 2017 she noticed a lump on the left of her neck. Neck ultrasound showed a 1.2X0.7X1.6 cm tumour mass within strap muscles. Calcium and PTH remained normal. CT imaging did not identify any other local recurrence or distal metastases. FNA was compatible with recurrent parathyroid disease. She underwent surgical resection in September 2017 and pathology demonstrated extension to the resection margins. She developed hypoparathyroidism postoperatively and she is now due to have local radiotherapy on the left.

Conclusion: Parathyroid carcinomas are rare endocrine tumours and therefore management in specialised centres in an MDT setting is of paramount importance. Although non-functioning parathyroid cancer is described, de-differentiation of a functioning tumour to non-functioning has not been reported previously.