Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Atypical parathyroid tumour masquerading as a large thyroid cyst  (#609)

Georgina Manos 1 , Jessica Preece 2 , John Burgess 1
  1. Department of Endocrinology and Diabetes, Royal Hobart Hospital, Hobart, Tasmania, Australia
  2. Department of Breast and Endocrine Surgery, Royal Hobart Hospital, Hobart, Tasmania, Australia

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Case:

A 59-year-old male presented with a right neck mass. Thyroid ultrasound demonstrated a well-defined avascular intrathyroidal unilocular hypoechoic cyst without solid component. Biochemistry showed primary hyperparathyroidism (table 1).  A 99mTc MIBI SPECT/CT showed low grade uptake in bilateral inferior poles and the superior right pole adjacent to the cystic structure but no definitive adenoma (figure 1). Thoracic x-ray revealed a T12 compression fracture. There was no other relevant personal or family history. Right hemithyroidectomy and bilateral exploration parathyroidectomy identified a large right-sided cyst and no parathyroid adenoma. Histology revealed a 50mm parathyroid tumour adherent to the thyroid with extensive fibrosis, tumour extension into the capsule and Ki67 of 2%, consistent with an atypical parathyroid tumour. Primary hyperparathyroidism resolved post-operatively. The patient will be followed up with 6-monthly PTH and calcium levels.

 

Discussion:

Atypical parathyroid tumours (APT) and parathyroid carcinomas (PC) account for 0.5-4% and 1.3% of cases of primary hyperparathyroidism respectively[1, 2]. APT demonstrate histologically atypical features including solid growth pattern, fibrous bands and adherence to surrounding structures but lack angio-, lymphatic and perineural invasion, local infiltration or metastases required to diagnose PC [3]. They present in younger patients and are associated with greater elevation of PTH and calcium and more frequent renal and bone manifestations compared with benign adenomas [1, 2, 4, 5, 6]. Ultrasound features include larger solid lesions, irregular shape, vascularity and heterogeneity [7]. The definitive diagnosis, as illustrated, is made histologically and has implications for postoperative management due to the different risk of recurrence and germline CDC73 mutation[4, 8]. The malignant potential of APT is unclear and long-term follow up is recommended.

This case highlights that importance of histopathological diagnosis in the setting of neck mass with primary hyperparathyroidism and explores predictors for recurrence and appropriate surveillance strategies.

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