HEAD & NECK IMAGING Iran J Radiol. 2017 April; 14(2):e41141. Published online 2017 February 25. doi: 10.5812/iranjradiol.41141. Research Article Rate of Malignancy in Exophytic Thyroid Nodules Fatma Dilek Dellal, 1,* Husniye Baser, 1 Dilek Arpaci, 2 Abbas Ali Tam, 3 Didem Ozdemir, 3 Aydan Kilicarslan, 4 Ersin Gurkan Dumlu, 5 Reyhan Ersoy, 3 and Bekir Cakir 3 1 Department of Endocrinology and Metabolism, Ataturk Training and Research Hospital, Ankara, Turkey 2 Department of Endocrinology and Metabolism, Bulent Ecevit University, Zonguldak, Turkey 3 Department of Endocrinology and Metabolism, Faculty of Medicine, Yildirim Beyazit University, Ankara, Turkey 4 Department of Pathology, Faculty of Medicine, Yildirim Beyazit University, Ankara, Turkey 5 Department of Surgery, Faculty of Medicine, Yildirim Beyazit University, Ankara, Turkey * Corresponding author: Fatma Dilek Dellal, Department of Endocrinology and Metabolism, Ankara Training and Research Hospital, Ankara, Turkey. Tel: +90-3122203052, Fax: +90-3122912525, E-mail: drdellal@yahoo.com Received 2016 August 03; Revised 2016 November 28; Accepted 2017 January 25. Abstract Background: There are ultrasonography (US) features suggested to be associated with a higher risk of malignancy in thyroid nod- ules. However, exophytic appearence of thyroid nodules has not been studied previously. Objectives: To evaluate US features, and cytological and histopathological findings in exophytic thyroid nodules. Patients and Methods: Patients with an exophytic thyroid nodule who underwent fine needle aspiration biopsy (FNAB) be- tween January and July 2015 were evaluated prospectively. Demographical data, US features, and cytology results were noted and histopathological findings were determined in operated patients. The results were compared with non-exophytic nodules of age and sex matched patients. Results: Data of 253 exophytic nodules in 247 patients and 529 non-exophytic nodules in 357 patients were analyzed. Hypoechogen- ity, mixed texture, and absence of peripheral halo were significantly higher in exophytic nodules (P < 0.001, P < 0.001, and P = 0.018, respectively). Nondiagnostic, atypia of undetermined significance/follicular lesion of undetermined significance and suspicious for malignancy cytology results were significantly higher in exophytic nodules (P = 0.002, P < 0.001 and P < 0.001 respectively). 6.7% of exophytic nodules and 1.9% of non-exophytic nodules had malignant cytology (P = 0.001). Histopathologically, 35 (47.9%) of 73 exophytic nodules and 18 (24.3%) of 74 non-exophytic nodules were malignant (P < 0.01). Capsular invasion was higher in the malignant exophytic group (53.5% vs 14.3%, P = 0.027). US features other than hypoechoic pattern which was higher in the malignant group were similar in benign and malignant exophytic nodules. Conclusions: Exophytic nodules seem to carry a higher rate of malignancy both cytologically and histopathologically. Suspicous US features except hypoechoic pattern were not higher in malignant compared to benign exophytic nodules. Keywords: Exophytic Appearance, Thyroid Nodule, Cytology, Histopathology, Thyroid Ultrasonography 1. Background The prevalence of thyroid nodules is very high in pop- ulation reaching 19-68% of randomly selected individuals when high-resolution ultrasonography (US) is used. Al- though the majority of nodules are benign and the malig- nancy rate is relatively low (7% - 15%), it is important to dif- ferentiate malignant and benign thyroid lesions (1). Fine needle aspiration biopsy (FNAB) of the thyroid is the gold standart diagnostic technique for determination of malignancy in thyroid nodules. It helps to avoid unnec- essary surgery; however, this procedure is invasive. US is a non-invasive, cheap, easy and sensitive method for de- tection of thyroid nodules. Although the diagnostic value of US to differentiate between benign and malignant nod- ules is limited, some US features were reported to be asso- ciated with a higher risk of malignancy (2). These features are hypoechoic pattern, solid texture, presence of micro- calcification, absence of peripheral halo, marginal irregu- larity, ratio of anterior-posterior to transvers diameter > 1, increased vascularity, and high strain index in elastosonog- raphy (3). There are different definitions for the term “exophytic” in the literature. By the most commonly used definition, exophytic tissue is defined as a tissue growing outside to- wards the surface epithelium of an organ or structure in which it is originating from (4). For thyroid tissue, exo- phytic nodule refers to a nodule that sticks out of the nor- mal thyroid boundary/outline. According to another defi- nition, a nodule that makes an acute angle with the adja- cent thyroid capsule could be called as exophytic nodule (5). Exophytic feature is often evaluated in many tumors. However, to our current knowledge, there is no study eval- uating the exophytic feature of thyroid nodules in the lit- erature. In this study, we aimed to determine US features, Copyright © 2017, Tehran University of Medical Sciences and Iranian Society of Radiology. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/) which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.