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Abstract

Case Presentation: A 40-year-old woman with primary hyperparathyroidism (pHPT) and unlocalized disease (negative neck ultrasonography and sestamibi scan) underwent neck exploration. Two borderline appearing inferior parathyroid glands were removed and a normal right superior gland was left in situ while the left superior gland was not identified. The removed parathyroid glands were of increased weight and histologically showed borderline hyperplasia. However, the postoperative calcium remained raised at over 3.0 mmol/L (2.2 to 2.6 mmol/L). A subsequent, 4-dimensional (4D) computed tomography (CT) scan failed to identify the parathyroid adenoma. Parathyroid angiography and venous sampling demonstrated no vascular blush, but significant elevation of parathyroid hormone (PTH) within the veins draining the left side of the neck. Extensive re-exploration of the left neck failed to identify a parathyroid gland and no drop in intraoperative PTH occurred after a left hemithyroidectomy. Repeated venous sampling was consistent with the source of PTH being within the left superior neck. Fluorine F 18-fluorocholine (FCH)-positive emission tomography (PET)/CT was undertaken and showed intense tracer uptake in a soft tissue focus (6 × 11 mm) lying within the carotid sheath just lateral to the proximal left internal carotid artery and medial to the internal jugular vein (Fig. 1). What is the diagnosis?