Case Report Fine-Needle Aspiration Cytology of Parathyroid Carcinoma Mimic Hürthle Cell Thyroid Neoplasm Chutintorn Sriphrapradang, 1 Pattana Sornmayura, 2 Niramol Chanplakorn, 2 Objoon Trachoo, 1 Pattarana Sae-Chew, 3 and Rangsima Aroonroch 2 1 Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, 270 Rama 6 Road, Rajthevi, Bangkok 10400, Tailand 2 Department of Pathology, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, 270 Rama 6 Road, Rajthevi, Bangkok 10400, Tailand 3 Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, 270 Rama 6 Road, Rajthevi, Bangkok 10400, Tailand Correspondence should be addressed to Chutintorn Sriphrapradang; chutins@gmail.com Received 8 June 2014; Revised 15 July 2014; Accepted 21 July 2014; Published 10 August 2014 Academic Editor: Osamu Isozaki Copyright © 2014 Chutintorn Sriphrapradang et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Background. Fine-needle aspiration (FNA) can cause misdiagnosis of cytomorphological fndings between parathyroid and thyroid lesions. Case Presentation. A 31-year-old man presented with a palpable neck mass on the right thyroid lobe. FNA cytology was reported as intrathyroidal lymphoid hyperplasia. Afer 5 years, repeated FNA was done on the enlarged nodule with result ofH¨ urthle cell lesion. Prior to right lobectomy, laboratories revealed elevated serum calcium and parathyroid hormone (PTH). Careful history taking revealed chronic knee pain and ossifying fbroma at the maxilla. Ultrasonography showed a 2.8cm mass inferior to right thyroid lobe. Pathology from en bloc resection was parathyroid carcinoma and immunohistochemical study revealed positivity for PTH. Genetic analysis found somatic mutation of CDC73 gene in exon1 (c.70delG) which caused premature stop codon in amino acid 26 (p.Glu24Lysfs ∗ 2). Te fnal diagnosis was hyperparathyroidism-jaw tumor syndrome. Conclusions. FNA cytology of parathyroid can mimic thyroid lesion. It is important to consider and correlate the entire information from clinical history, laboratory, imaging, and FNA. 1. Introduction Parathyroid carcinoma is a rare malignancy, afecting less than 1% of patients with primary hyperparathyroidism [1, 2]. It is usually associated with severe clinical presentations with markedly elevated levels of serum calcium >14 mg/dL and parathyroid hormone (PTH) levels from >5 to 10 times the upper normal limit [3]. Terefore, almost all the patients are symptomatic at the time of presentation [4]. However, it can be an indolent tumor with subtle manifestation reported in 2–7% and up to 30% in the previous case series [5–7]. Patients with parathyroid carcinoma frequently present with a palpable neck mass that can masquerade as a thyroid nodule because of the close localization [8]. Te fne-needle aspi- ration (FNA) can cause misdiagnosis of cytomorphological fndings because of signifcant overlap in cytological features of parathyroid and thyroid lesions. Oncocytic parathyroid adenoma can be confused with H¨ urthle cell thyroid neo- plasm, especially in the absence of clinical information [9]. A high prevalence of parathyroid carcinoma has been demonstrated in patients with hyperparathyroidism-jaw tumor syndrome (HPT-JT; OMIM#145001). It is an exceed- ingly rare cancer syndrome characterized by primary hyper- parathyroidism, ossifying fbromas of the maxilla and mandible, and less commonly renal hamartoma, Wilms’ tumor, polycystic kidney disease, degenerative cysts, and/or uterine tumors. Primary hyperparathyroidism is usually the presenting manifestation occurring in late adolescence or in young adulthood. Approximately 15% of these cases have parathyroid carcinoma. A germline inactivating mutation Hindawi Publishing Corporation Case Reports in Endocrinology Volume 2014, Article ID 680876, 7 pages http://dx.doi.org/10.1155/2014/680876