LAUSR

A 15-year-old boy was noted to have incidental hypercalcaemia (peak serum corrected calcium 3.09 mmol/L, normal 2.20–2.65) during an episode of acute pharyngitis. His medical history was unremarkable and there was no family history of endocrinopathies. Aside from the pharyngitis, his examination was reassuring and there were no dysmorphic features. Further investigations showed an elevated parathyroid hormone level of 18 pmol/L (normal 1–7). Other pertinent investigations were normal, including creatinine, thyroid function, calcitonin, 25-hydroxy-vitamin D levels, plasma and urine metanephrines. Ultrasonography showed enlargement of the left superior parathyroid gland (12 mm × 7 mm × 5 mm) suggestive of an adenoma. There was an unexpected finding of a large (80 mm × 10 mm × 16 mm) mass with very heterogeneous internal echotexture including small, well-defined ovoid nodules with more homogenous echotexture anterior to the left carotid sheath extending from the base of the skull to the thoracic cavity. The appearance of the mass was concerning for a second neoplasm such as paraganglioma related to the left sympathetic chain. The coexistence of a parathyroid mass raised suspicion of multiple endocrine neoplasia (MEN) syndrome. Tc99m sestamibi scintigraphy confirmed a parathyroid adenoma posteromedial to the upper pole left lobe of the thyroid. Magnetic resonance imaging (MRI) performed to assess the second mass showed a contrast-enhancing T2-hyperintense lesion (83 mm × 10 mm × 7 mm), extending from the level of C3 vertebrae to the level of the aortic arch. The location and imaging characteristics suggested a paraganglioma. There was no splaying of the carotid arteries and no skull base extension. The brain appeared normal with a preserved pituitary bright spot. There was no abnormal uptake elsewhere. F18 fluorodeoxyglucose position emission tomography (PET) computed tomography scan showed low-grade uptake within the left carotid sheath mass with no other regions of abnormal uptake, and Ga68-DOTATATE PET computed tomography scan showed physiological tracer uptake throughout the body (Fig. 1). What is the most likely differential for the carotid sheath mass? (Answer on page 205)