SAT207 Parathyroid Carcinoma: A Case Report

Disclosure: K.T. Sy: None. Background: Parathyroid carcinoma is a rare malignancy, accounting for less than 1% of causes of primary hyperparathyroidism. Case reports have mentioned of parathyroid carcinoma arising in patients with prior neck irradiation, in secondary and tertiary hyperparathyroidism and in patients with history of thyroid cancer and parathyroid adenoma. However, none of these reported associations have been completely established. Clinical Case: The is a case of a 59-year old male presenting with hypercalcemia. He was diagnosed with primary hyperparathyroidism secondary to a parathyroid adenoma, underwent parathyroidectomy with resolution of the hypercalcemia. Six years later, patient had recurrence of hypercalcemia with elevated PTH levels. Parathyroid imaging revealed a mild sestamibi-avid focus in the left retrosternal region, suggestive of an ectopic parathyroid gland and radio-guided neck exploration was done with excision of lesion. Histopathological report revealed parathyroid carcinoma. Two years later, there was recurrence of parathyroid carcinoma but mediastinal exploration revealed no lesions consistent with parathyroid carcinoma. Hypercalcemia with hyperparathyroidism persisted, and cinacalet was started but the patient could not tolerate the nausea associated with the medication. Repeat parathyroid imaging revealed sestamibi-avid lesions in the right retroclavicular, left prevascular/retrosternal, and a left paratracheal areas. Surgical exploration was offered but the patient refused. The patient also developed hypertension and low bone density was noted on dual X-ray absorptiometry (DXA) scan. He was started on denosumab 60 mg subcutaneously every 6 months, which was increased to 60mg every month and then 120mg every month to maintain normal calcium levels. The patient also developed chronic kidney disease, eventually requiring hemodialysis for elevated creatinine levels and hypercalcemic crisis. Soon after hemodialysis was started, the patient had a myocardial infarction and eventually expired. Conclusion: Complete surgical resection is the primary mode of therapy in parathyroid carcinoma, although hypercalcemia is the main cause of morbidity and mortality, rather than the tumor burden. The adjuvant use of radiotherapy and chemotherapy are still controversial. Some studies have shown that long term survival is favorable, but recurrences are frequent and patients tend to live a life filled with long-term follow up, multiple laboratory exams and imaging, hospitalizations and frequent reoperations. Mortality is usually due to uncontrollable hypercalcemia, leading to renal failure and cardiac arrhythmias. Presentation: Saturday, June 17, 2023