LAUSR

Hyperparathyroidism due to a parathyroid adenoma was the aetiology of this child’s hypercalcaemia. The presence of a second lesion raised several possibilities, although given the proximity to the vasculature, consideration was given to paraganglioma, a group of neuroendocrine tumours that originate from either the parasympathetic or sympathetic nervous system. Paraganglial head and neck tumours are typically non-functional in children. If functional, mutations in the succinate dehydrogenase subunit account for most head and neck tumours. Other genetic syndromes in order of likelihood include MEN type 2, MEN type 1, von Hippel–Lindau syndrome and neurofibromatosis type 1. In this case, genetic testing for MEN2A, undertaken in the context of coexisting hyperparathyroidism, returned with no mutations detected. Several imaging modalities are available and provide useful additional information for head and neck tumours, if interpreted within the clinical context. In this case, the ultrasonography characteristics, as well as findings of a T2-hyperintense contrastenhancing lesion on MRI supported an initial diagnosis of paraganglioma. However, literature has shown that over 90% of paraganglioma cases have positive DOTATATE uptake which was not observed in this case. Review of the ultrasonography images at a multidisciplinary team meeting raised the question of whether the second lesion could be thymus. At the time of the left superior parathyroidectomy, a biopsy of the carotid sheath mass was pursued, with careful medical planning to confirm that the carotid sheath mass was non-secretory and surgical planning to avoid damage to surrounding structures. Histological analysis for the carotid sheath mass revealed thymic tissue. The thymus is a lymphatic organ that arises from the third and fourth pharyngeal pouch, similar to the parathyroid glands. It migrates caudally along the thymopharyngeal duct, and ectopic thymic tissue can occur at various points along this descent, as well as around the major vessels. Remnant cervical thymus can present at any age and has been reported in more than twothirds of children; it tends to increase in size during childhood before involution occurs eventually in adolescence. Thymic remnants can form cysts during physiological atrophy, which accounts for 0.3% of all congenital cervical cysts in children. Thymic cysts or hyperplasia do not typically warrant surgical Fig 1 Barium swallow test showing immediate and bilateral barium inhalation and large hiatus hernia.