A CASE OF SEVERE HYPERCALCAEMIA SECONDARY TO PARATHYROID CARCINOMA

Abstract

INTRODUCTION
Parathyroid carcinoma is a rare malignancy, accounting for only 0.005% of all cancers and about 0.5-1% of parathyroid disorders with similar incidence in male and females. It usually presents with manifestations of severe hypercalcaemia with bone involvement and nephrolithiasis, associated with markedly raised parathyroid hormone; although presentations can be variable.

CASE
We report a case of a 44-year-old Chinese male with underlying hypertension, chronic kidney disease stage 3A (eGFR 52 mL/min/1.73 m2) who was incidentally found to have PTH–dependent severe hypercalcaemia (corrected calcium 4.56 mmol/L), hypophosphataemia with iPTH 102.1 (>7 times the upper limit of normal) during admission for left cheek subcutaneous abscess. Hypercalcaemia was managed with calcitonin, bisphosphonate alongside aggressive saline diuresis resulting to a serum calcium of 2.85 mmol/L. Ultrasound of the neck showed a well-defined ovoid hypoechoic lesion, caudal to the lower pole of the left thyroid lobe measuring 1.4 x 1.5 x 2.0 cm consistent with left parathyroid adenoma, which was confirmed with parathyroid Sestamibi scintigraphy. Ultrasound of the kidneys revealed no nephrolithiasis while bone densitometry showed severe osteoporosis at the distal third of forearm and left neck of femur with T score -4.1 and 3.0 respectively. Surgical excision of the left parathyroid with intraoperative PTH monitoring was done with subsequent removal of the lesion leading to normalization of the PTH level. Histopathology examination revealed lymphovascular permeation with irregular nodular proliferation of parathyroid cells with transgressed boundaries which are features compatible with parathyroid carcinoma. Post operatively, the patient was normocalcaemic but declined further surgical tumour clearance.

CONCLUSION
This case highlights the need for a high index of clinical suspicion for the presence of parathyroid carcinoma pre-operatively in patients who exhibit severe hypercalcemia, markedly raised PTH and bone manifestations so that en bloc-resection of the parathyroid with ipsilateral partial thyroidectomy and central node dissection can be planned prior to surgery.