Poster Presentation ESA-SRB 2023 in conjunction with ENSA

Parathyroid cyst: an uncommon cause of primary hyperparathyroidism (#314)

Sneha Krishna 1 , Adam Morton 1
  1. Mater Hospital Brisbane, South Brisbane, QLD, Australia

Introduction

Parathyroid cysts (PTC) represent <0.5% of parathyroid gland pathology and 1-5% of neck masses.1 A case of a large functioning PTC is presented.

Case

A 41-year-old man presented with recurrent non-obstructive ureteric calculus and symptomatic hypercalcaemia.

Biochemistry revealed corrected calcium 3.42mmol/L (2.10-2.60), ionised calcium 1.89mmol/L (1.13-1.3), PTH 49pmol/L (2.0-9.5), serum creatinine 163umol/L (60-110), 25-OH vitamin D 67nmol/L (50-150) and 24-hour urine calcium 5.0mmol/24hr (1.2-7.5) consistent with primary hyperparathyroidism. Neck ultrasonography and 4D-CT showed non-enhancing 71x37x33mm cystic lesion inseparable from the inferior margin of the left thyroid lobe, reported as being consistent with a colloid thyroid nodule. Cyst aspirate yielded 50mls of fluid with PTH 167450pmol/L consistent with parathyroid cyst adenoma (PTCA). Sestamibi study post-aspiration revealed a discordant focus of activity adjacent to the inferior pole of left thyroid lobe. No pathogenic variants were detected in CDC73, CDKN1B, MEN1 or RET genes. 

He was treated with intravenous fluids and pamidronate 60mg with normalisation of renal function and corrected calcium to 2.39mmol/L. Hypercalcaemia recurred three weeks later requiring further pamidronate. A 6.9g partially cystic fibroadipose tissue measuring 60x30x10mm was surgically removed with ~40% of tissue remaining in situ. Histopathology was consistent with benign parathyroid adenoma with cystic changes. 

Discussion

PTCs may present as an incidental neck mass (41.7%), with compressive symptoms (20.6%), or with symptomatic hypercalcaemia (6.5%). PTCs are functional (PTCA) with hypercalcaemia in 17.5% of cases, and nephrolithiasis in 2.8%.1 PTCAs account for 1-2% of cases of primary hyperparathyroidism.2

Functioning and non-functioning parathyroid carcinoma has been described within PTCs.3 Surgical excision is recommended where PTCs are functional/hypercalcaemic, symptomatic, with uncertainty of diagnosis/suspicion of malignancy, with mediastinal disease or with recurrence following fine-needle aspiration. Intraoperative parathyroid hormone levels may be unreliable due to prolonged decay presumed due to microscopic leakage of cyst fluid with subsequent absorption by surrounding tissue.4

  1. Papavramidis TS, Chorti A, Pliakos I, Panidis S, Michalopoulos A. Parathyroid cysts: A review of 359 patients reported in the international literature. Medicine (Baltimore). 2018;97(28):e11399. doi:10.1097/MD.0000000000011399
  2. Rosenberg J, Orlando R, 3rd, Ludwig M, et al. Parathyroid cysts. Am J Surg 1982; 143: 473-480. 1982/04/01. DOI: 10.1016/0002-9610(82)90198-2
  3. Vazquez FJ, Aparicio LS, Gallo CG, et al. Parathyroid carcinoma presenting as a giant mediastinal retrotracheal functioning cyst. Singapore Med J 2007; 48: e304-307. 2007/11/03
  4. Chow TL. Intraoperative parathyroid hormone assay for parathyroid cyst - be cautious. Eur Ann Otorhinolaryngol Head Neck Dis 2021; 138: 513-514. 2021/04/19. DOI: 10.1016/j.anorl.2021.01.005
  5. Chow TL. Intraoperative parathyroid hormone assay for parathyroid cyst - be cautious. Eur Ann Otorhinolaryngol Head Neck Dis 2021; 138: 513-514. 2021/04/19. DOI: 10.1016/j.anorl.2021.01.005