Metastatic parathyroid carcinoma: A tale of refractory hypercalcemia

Abstract

Background/objective: Parathyroid carcinoma is a rare entity presenting as parathyroid hormone (PTH) dependent hypercalcemia. Our objective was to report a case of metastatic parathyroid carcinoma in a middle-aged woman, who presented with refractory hypercalcemia and the strategies we used to induce remission. Case report: A 47 year old lady with a past history of a left superior parathyroid adenoma excision, presented with recurrent PTH dependent hypercalcemia. An ultrasonography of the neck and parathyroid scintigraphy were normal. Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) scan picked up metabolically active lesions in the lingular segment of the left lung and another lesion in the diaphragmatic pleura of the left hemi-thorax. Following metastectomy of the lung nodules, she developed symptomatic hypocalcemia with a reduction of serum PTH levels. The histopathology and immunoprofile were consistent with metastatic carcinoma. The PTH levels started rising 2 months after the surgery, with calcium levels remaining stable on cinacalcet, denosumab and cabozantinib. Discussion: Parathyroid carcinoma is a rare endocrine malignancy with typically indolent, yet progressive course. There is no consensus on the treatment and follow-up of parathyroid carcinoma, owing to its rarity. The greatest likelihood of cure is achieved if complete resection of all malignant tissue is successful at the time of initial surgery. Surgical reduction of the tumor mass may also render the patient's hypercalcemia more amenable to medical treatment with hydration, potent intravenous bisphosphonates, denosumab and cinacalcet. Conclusion: Surgical debulking of the metastatic lesions, followed by medical management of hypercalcemia offers promising results in the management of metastatic parathyroid carcinoma.

Keywords

• Refractory hypercalcemia
• Parathyroid carcinoma
• Denosumab
• Scintigraphy
• Hyperparathyroidism