A Rare Co-Occurrence of Parathyroid and Papillary Thyroid Carcinoma

Introduction: Although co-occurring thyroid pathologies are common in patients with primary hyperparathyroidism, synchronous parathyroid and differentiated thyroid carcinoma is a rare situation. Case: A 65-year-old woman presented to our endocrinology clinic for evaluation of hypercalcemia. She had an albumin-corrected serum calcium (Ca) concentration of 12.4 mg/dl (normal, 8.6-10 mg/dl), serum phosphorus (P) concentration of 2.2 mg/dl (normal, 2.4-5.1 mg/dl), and intact parathyroid hormone (iPTH) concentration of 437 pg/ml (normal, 12-88 pg/ml). Ultrasound revealed thyroid nodules and a parathyroid adenoma. Histopathology showed a parathyroid carcinoma in the left lower parathyroid gland and a co-occurring multifocal papillary carcinoma on both sides of the thyroid gland. Conclusion: Here we describe a patient with synchronous parathyroid carcinoma and papillary thyroid carcinoma. Thyroid lesions, including differentiated cancers, may occur together with parathyroid lesions, suggesting the need to evaluate the thyroid gland in patients with primary hyperparathyroidism.