Endocrine Abstracts

Introduction: Intrathyroidal parathyroid adenomas (IPA) are a rare cause of primary hyperparathyroidism (PHP) and their differential diagnosis includes other parathyroid and thyroid lesions. Although <7% of parathyroid adenomas are intrathyroidal, this location represents almost 20% of ectopic cases and their preoperative identification can pose difficulties, often being an intraoperative finding.

Clinical case: A 70-year-old woman diagnosed with breast carcinoma in remission, nephrolithiasis, osteopenia, vitamin D deficiency and hypertension, was evaluated to complete the study of PHP detected in September 2016. In the laboratory tests the following was observed: calcium 12.56 mg/dl, albumin 4 g/dl, PTH 335.2 pg/ml, 25-OH-vitamin D 20 μg/l, phosphorus 2 mg/dl; renal and thyroid function were normal. The cervical CT showed ‘indeterminate’ hypodense thyroid nodules whose size ranges from 7 to 10 mm and the Tc99 m-sestamibi scintigraphy, a nodule in the left thyroid lobe with little probability of corresponding to a parathyroid adenoma. Therapy with cinacalcet was started but, at a 60/90 mg/day alternation, it did not control calcium and PTH, and more imaging tests were performed. In the 2nd cervical CT, 2 nodules<1 cm were identified in the right thyroid lobe and a nodular lesion of 1.2×1.4×2.8 cm, with a central cystic area measuring 0.4×1.7 cm of tubular morphology and thickened walls in the left thyroid lobe. Thyroid ultrasonography-guided fine-needle-aspiration (US-FNA) showed multiple nodules<1 cm in both thyroid lobes and the nodule described in the left lobe, of 3.12×1.26×1.14 cm, was heterogeneous, lobed, with thick hypoechoic halo and increased peripheral flow, and was sonographically suspicious. The cytology was compatible with parathyroid tissue and negative for malignant cells and PTH in the wash fluid was >3,230 pg/ml with a wash fluid/serum PTH ratio>18. In August 2018, left hemithyroidectomy was performed and total and ionic calcium were normal 1 day later; PTH was 3.4 pg/ml. Histopathological diagnosis: Intrathyroid parathyroid adenoma associated with nodular hyperplasia.

Discussion: In this patient, the IPA was identified by US-FNA cytology but, according to literature, this test is not always useful in recognizing the parathyroid origin of an intrathyroid nodule and PTH estimation in aspirate had an important role in diagnosis. Especially when there is concomitant thyroid pathology or it is necessary to rule out malignancy, application of both methods facilitates planning minimally invasive parathyroidectomy techniques.