Endocrine Abstracts

JOINT747

Background: Parathyroid carcinoma is an extremely rare endocrine malignancy, comprising less than 1% of primary hyperparathyroidism cases and only 0. 005% of all cancers. Its clinical presentation and symptoms primarily result from hypercalcemia rather than from local invasion or distant metastasis.

Material and methods: A retrospective study was performed, analysing all histopathologically confirmed cases of parathyroid carcinoma identified among primary hyperparathyroidism cases between 2004 and 2024. The demographics and clinical characteristics of these parathyroid carcinoma cases were compared to a randomly selected group of parathyroid adenoma cases in a 2:1 ratio. Clinical and laboratory parameters of all parathyroid carcinoma cases were thoroughly evaluated.

Result: In our study, the prevalence of parathyroid carcinoma was 3% (n = 16) among all diagnosed cases of primary hyperparathyroidism. The mean age at presentation was 50. 3±11 years in the carcinoma group and 47±18 years in the adenoma group. Males were predominant in the parathyroid carcinoma group, while females were more prevalent in the adenoma group. Compared to parathyroid adenoma, carcinoma cases showed more palpable masses (82% vs. 6. 3%; P < 0. 001), higher rates of gastrointestinal symptoms, nephrolithiasis, pancreatitis. One patient had reversible Mobitz Type 1 heart block in carcinoma group. Investigations showed that carcinoma group had lower albumin (3. 6±0. 8 g/dL vs. 4. 2±0. 7 g/dL; P < 0. 01), and higher serum creatinine (1. 4±0. 6 mg/dL vs. 1. 1±0. 5 mg/dL; P < 0. 05). In patients with parathyroid carcinoma mean levels of calcium, phosphorus, alkaline phosphatase, iPTH and vitamin D were 13. 7±2. 1 mg/dL, 2. 3±0. 6 mg/dL, 301±169 IU/l, 123. 3±137 pmol/l, 43. 5±32. 2 nmol/l respectively (no significant difference from parathyroid adenoma). Mean size of involved parathyroid gland in USG was 2. 7±1. 1 cm. Most involved gland was inferior parathyroid. Histopathology of the carcinoma group revealed capsular invasion (88%), vascular invasion (68%), necrosis (88%), mitotic figures (50%), and perineural invasion (63%). Predictor of risk factors for parathyroid carcinoma were palpable mass and gland size >3 cm. All patients underwent surgical resection, with additional treatments including cinacalcet 3 (19%), radiotherapy 3 (16%), and TACE 1 (6%). Recurrence was observed in 5 (31%) patients.

Conclusion: Palpable neck mass, gland size >3 cm were key predictors of parathyroid carcinoma, while recurrence was predicted by calcium >14 mg/dL, gland size >3 cm, and extrathyroidal extension with recurrence rate of 31%.