Parathyroid carcinoma accounts for 0.5-5% of primary hyperparathyroidism, and is exceptional in Chronic Kidney Disease. It usually presents with Hypercalcemia and increased PTH. Image studies with 99Tc-sestaMIBI scintigraphy and ultrasonography are first line. Histopathological features and negative immunohistochemistry staining for parafibromin provide the definitive diagnosis. Summary: A 49-year-old male with stage 5 CKD presented with Hypercalcemia and a rapid rise in PTH levels. Image

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... s showed signs of parathyroid hyperplasia. After subtotal parathyriodectomy, intraoperative PTH levels did not fall, and a fifth ectopic gland in the mediastinum was resected. Biopsies were consistent with parathyroid carcinoma. Conclusion: Parathyroid carcinoma is an infrequent pathology in CKD, and should be considered in patients with sudden rises in calcium and/or PTH levels. Image studies are highly sensitive, but false negatives exist. Unsatisfactory decreases in intraoperative PTH levels suggest an ectopic gland, and may provide the key to a successful surgery.