Endocrine Abstracts

Introduction: Pre-operative localization of parathyroid adenoma is generally done by two localization studies: ultrasonography (US) and parathyroid scintigraphy using 99 m-techentium sestamibi SPECT with CT (Tc-MIBI SPECT/CT), which also report on Incidental thyroid nodules. The aim of our retrospective study was to determine the incidence, characteristics and outcomes of these incidental thyroid findings during parathyroid imaging.

Method: A database of all patients who underwent parathyroid surgery over 2 years (2017-2019) was derived from ENT department. As per local clinical practice, all patients had pre-operative localization with US and Tc-MIBI SPECT/CT. Patients with tertiary hyperparathyroidism were excluded. Clinical details including thyroid function status, outcomes of imaging, referral for further investigations such as FNA and their outcomes were collected. Suspicious thyroid nodules were investigated as per standard clinical practice and local thyroid MDT decisions.

Results: A total of 111 patients were included for analysis. The anatomical outcomes were: Normal gland 52, ectopic thyroid gland 2, unclassified nodules including multinodular goitre 14, benign thyroid nodule not requiring further investigation (graded as U2 on US) 31 and nodules requiring further investigation (graded U3 or above on US). FNA of these 12 patients showed: thyroid carcinoma 7(4 papillary and 3 follicular variant), benign intra-thyroid parathyroid adenoma 3, hyperplastic nodule 1 and lymphocytic thyroiditis 1. All patients with thyroid carcinoma proceeded to total thyroidectomy as per MDT outcome.

On the Tc-MIBI SPECT/CT, 8 patients showed heterogeneous or reduced thyroid uptake, including 3 out of 7 thyroid carcinoma patients proceeding for biopsy and 1 lymphocytic thyroiditis all these patients were on thyroxine replacement. One patient with hyperplastic nodule showed persistent intense uptake while rest 102 patients showed homogenous and symmetrical uptake and were biochemically euthyroid.

Conclusion: A significant number of incidental thyroid findings are identified during parathyroid localization imaging. Our study showed 11% that required further investigations with incidental diagnosis of thyroid cancer.