Large Undescended Inferior Parathyroid Adenoma Masquerading as part of Retropharyngeal Large Multinodular Goitre
A Plonczak, A N Di Marco, F F Palazzo, Department of Thyroid & Endocrine Surgery, Hammersmith Hospital, Imperial College Healthcare NHS Trust
The Case: A 71 year old female with asymptomatic biochemically proven primary hyperparathyroidism and compressive symptoms from a very large toxic multinodular goitre is presented. Examination revealed a very large goitre with distension of the external jugular veins suggestive of thoracic inlet compression. Localisation studies in the form of ultrasound neck and SestaMIBI failed to identify a parathyroid adenoma. CT of the neck and upper thorax noted the left thyroid lobe to be larger with a significant retropharyngeal component, extrathoracic tracheal compromise and minor retrosternal extension.
A combined total thyroidectomy and parathyroidectomy via a cervical approach was performed. The right thyroid lobe was mobilised first, during which an enlarged right superior parathyroid gland was identified. The left lobe of the thyroid was then mobilised and a classically positioned but abnormally large left superior parathyroid gland was found and safely removed. Subsequently, during mobilisation of the highly developed superior pole of the left thyroid lobe, a separate retropharyngeal structure, superomedial to the lobe, was encountered and mobilised. This structure, measuring up to 63mm, appeared to be separate from the thyroid and was recognised as a very large adenoma of what we interpret as a non-descended left inferior parathyroid gland.
Post operative recovery was uneventful, including normalisation of biochemistry. Histology showed a multinodular goitre with an incidentally found 0.2mm papillary thyroid carcinoma and hyperplasia of all three parathyroid glands, including the very large (21g) non-descended left inferior gland.
Discussion: The largest adenoma in this case was many hundreds of times the size of a non-pathological gland. Giant parathyroid adenomata are defined as weighing ≥35g and are not necessarily functional1. The location of this gland was characteristic of a non descended inferior gland. These occur in <1% of cases. Coexistent thyroid and parathyroid pathology is not unusual, with rates of synchronous parathyroid and thyroid surgery in patients with PHPT reported in up to 29%2. Despite this, we believe this case to be unique in the published literature given the huge goitre, unusual nature of the parathyroid disease and coincidentally found microcarcinoma. However, the primary value of this case lies in the illustration of the difficulties of parathyroid localisation in the presence of a large goitre.
1. Spanheimer PM et al. Do giant parathyroid adenomas represent a distinct clinical entity? Surg (United States). 2013;154(4):714–9.
2. Ryan S et al. Co-existent thyroid disease in patients treated for primary hyperparathyroidism: implications for clinical management. Eur Arch Otorhinolaryngol [Internet]. 2015;272(2):419–23.