Giant Cystic and Mediastinal Parathyroid Adenoma with Non-Uptake in Scintigraphy

Introduction: In 85% of patients, the cause of Primary Hyperparathyroidism (PHPT) is an adenoma. Parathyroid adenoma localization is usually simple. 96% of localizations prior to surgery are achieved with ultrasound and scintigraphy combination. Difficulties can appear. If the gland is not located in a cervical position and has no uptake in scintigraphy but there is high suspition of an adenoma causing the PHPT, some extra tests should be considered. Case Report: We present a case of giant cystic mediastinal adenoma, a quite rare condition, which was diagnosed as a thyroid colloid cyst by ultrasound, and was not localized by scintigraphy. We report the CT scan and the magnetic resonance imaging (MRI) images that show the tumour. It was surgically resected by a cervical approach. After the excision, the patient recovered normal levels of Calcium and Parathormone (PTH). Conclusion: We review literature about cystic and mediastinal adenomas and diagnostic methods when the standard ones do not give an accurate localization diagnosis.