Endocrine Abstracts

Parathyroid carcinoma (PC) is a rare malignancy, with fewer than 1,000 cases reported since 1904. It accounts for approximately 0.005% of all cancers and 0.5–1% of parathyroid disorders.

Case: A 52-year-old male was referred to the Endocrine clinic in 2023 for severe hypercalcemia (Ca 3.2 mmol/l). Biochemistry: Ca 3.2mmol/L PTH 32.42 pg/mL, Creatinine at 130 μmol/l. He had a background of primary hyperparathyroidism treated with L parathyroidectomy with concordant pre-operative U/S in 2019 at a different center. Surgical notes suggested the lesion was adherent to surrounding structures, with histology confirming atypical features. Hypercalcemia recurred 1 year post surgery, unfortunately patient did not engage with specialist services. Patient underwent localization studies, while suspecting parathyroid malignancy. MRI neck, 4D CT, ultrasound neck repeated on 2 occasions were inconclusive. CT-TAP identified bilateral pulmonary nodules suggestive of metastasis, confirmed by a Choline PET scan. A diagnosis of metastatic parathyroid cancer was confirmed in a multidisciplinary meeting. The metastatic lesions are unresectable currently. The management of hypercalcemia has been challenging, requiring multiple admissions, however he is responding to Denosumab injections currently.

Discussion: Parathyroid carcinoma often presents with severe hypercalcemia, frequently exceeding 3.5 mmol/l, and elevated PTH > five times the normal. There is significant renal and bone disease compared to those with parathyroid adenoma. The diagnosis of parathyroid carcinoma can be challenging histologically, but macroscopic features intraoperatively and clinical progression can support the diagnosis.

Conclusion: Our case is quite unusual and challenging in view of the presentation with distant metastasis with no localized disease. It highlights the importance of considering parathyroid carcinoma in patients with persistent severe hypercalcemia. Early diagnosis and surgical intervention are essential for improving patient outcomes. The management of refractory hypercalcemia remains a significant challenge.