A 55-year-old woman presents with severe hypercalcemia (serum calcium 14.2 mg/dL), markedly elevated PTH (980 pg/mL), and a palpable neck mass. Sestamibi scan shows a 3.5 cm inferior parathyroid lesion. Preoperative laryngoscopy shows left vocal cord palsy. What is the most likely diagnosis?

• A Primary hyperparathyroidism due to parathyroid adenoma
• B Parathyroid carcinoma ✓
• C Tertiary hyperparathyroidism
• D Familial hypocalciuric hypercalcemia (FHH)

Explanation

Parathyroid carcinoma should be suspected when serum calcium is markedly elevated (>14 mg/dL), PTH is disproportionately high (often >3 times upper limit), a palpable neck mass is present, and there is associated vocal cord palsy from recurrent laryngeal nerve invasion. These features are atypical for a benign adenoma. FHH presents with mild hypercalcemia and low urinary calcium.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.