Introduction: Parathyroid carcinoma is a rare endocrine malignancy found in 1–5% of patients with primary hyperparathyroidism. It commonly presents with severe hypercalcemia and markedly elevated parathyroid hormone (PTH) levels. We report a challenging case of parathyroid carcinoma presenting with refractory hypercalcemia with incidental papillary thyroid microcarcinoma. Case: A 63-year-old female with hypertension, diabetes mellitus, dyslipidemia, and ischemic heart disease had been followed for primary hyperparathyroidism since 2014 (PTH5.5 pmol/L, calcium range 2.3–4.7 mmol/L). Initial neck ultrasound was suggestive of parathyroid adenoma over left side, but parathyroid scintigraphy failed to localize a lesion. She refused surgical intervention initially until April 2025, then she later agreed. Re-evaluation prior to operation revealed PTH level 76 pmol/L, and repeated parathyroid scintigraphy showed mild sestamibi avid uptake on left thyroid nodule. While awaiting surgery, she was admitted with a hypercalcemic crisis (serum calcium 3.7–5.38 mmol/L), complicated with acute kidney injury. Repeated ultrasound neck revealed extrathyroidal lesion adjacent to inferior pole of left thyroid (1.6 × 1.7 × 1.2 cm). She required aggressive intravenous hydration, intravenous pamidronate, calcitonin, and Denosumab to optimize her calcium level peri-operatively. She underwent left neck exploration with en-bloc left inferior parathyroidectomy, left hemithyroidectomy, and central neck dissection in November 2025. Histopathological examination confirmed parathyroid carcinoma (pT3N1) with nodal metastasis (1/4 lymph nodes positive) and an incidental papillary thyroid microcarcinoma measuring 1 mm (pT1a). Conclusion This case highlights the challenges of perioperative hypercalcemia management in parathyroid carcinoma. Effective preoperative control often requires multiple treatment modalities. Severe refractory hypercalcemia and high PTH level should raise a high index of suspicion for malignancy. Early complete resection is the cornerstone of treatment and is associated with optimal outcomes.
Papillary Thyroid Microcarcinoma ; Calcium ; Parathyroid Neoplasms