Ectopic Retrolaryngeal Parathyroid Adenoma Detected by 18F-Ethylcholine PET/US Fusion Imaging

A 68-year-old woman was referred with the diagnosis of symptomatic pHPT (primary hyperparathyroidism). Ultrasonography (US) and 99mTc-MIBI scintigraphy could not clearly identify a parathyroid adenoma. A primary unilateral surgical exploration remained unsuccessful to remove adenomatous parathyroid tissue and the pHPT persisted. 18F-ethylcholine PET/CT showed a left-sided retropharyngeal lesion with intense tracer uptake that could not be detected on US images at first sight. Therefore, additional 18F-ethylcholine PET/US fusion imaging was performed and revealed a poorly definable nodular structure on US that could be unambiguously correlated to the PET finding. Surgical excision confirmed an oncocytic variant of parathyroid adenoma, and parathormone and calcium levels normalized immediately.