Clinicopathological features and ultrasonographic findings of thyroid nodules classified as atypia of undetermined significance/follicular lesion of undetermined significance

Atypical thyroid nodule findings




AUS/FLUS, thyroid cancer, ultrasonography


Objective: The Bethesda reporting system (BRS) is used as a standard in the evaluation of thyroid fine needle aspiration cytology. Atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is defined as Bethesda category III and the malignancy risk is reported to be 5-15%. Nodules diagnosed with AUS/FLUS remain uncertain in terms of malignancy risk. Our aim is to determine the malignancy risk of aspirations classified as AUS/FLUS in our hospital, where thyroid fine-needle aspiration cytology (FNAC) is performed frequently and to examine whether there is a relationship between ultrasonographic data and the diagnosis of AUS/FLUS.

Methods: The data of 3200 patients who were followed up in our hospital between 2008 and 2018 for thyroid nodules and underwent FNAC were analyzed. There were 150 patients with thyroid nodules diagnosed with AUS/FLUS in this patient group. The clinical information, radiological findings and surgical treatment process of these patients were documented using our hospital database.

Results: A total of 150 out of 3200 cases were diagnosed with AUS/FLUS. Of the patients classified as AUS/FLUS, 13.3% (20/150) underwent immediate surgery and 31.3% (47/150) were followed up with only ultrasonography (US). FNAC was repeated in 62.4% (83/150) of them. Ten percent (16/83) of the group whose FNAC was re-examined were inadequate and 27.3% (41/83) were benign. A second diagnosis of AUS/FLUS was conducted in 26.51% (22/83) of them (14.7% (22/150) of all patients) and 4.82% (4/83) of them (2.7% (4/150) of all patients) were diagnosed with suspected malignancy. The group that was diagnosed with two consecutive AUS/FLUSs and suspected malignancy underwent surgery. In the operated group, 26.08% (12/46) were diagnosed with malignancy. In terms of ultrasonography data, only macrocalcification (41.7% (n: 5/12)) supported the diagnosis of malignancy (p<0.001). In terms of AUS/FLUS, our study did not observe ultrasonographic data to support this diagnosis (p>0.05).

Conclusion: We believe that the place of FNAC is very important in the approach to thyroid nodules. We recommend that the decision to directly undergo surgery or to send cytology for the second time in cases where AUS/FLUS is detected for the first time in the cytology taken from the patients should be made by the following clinician. In addition, we should emphasize that FNAC and US have an important place in early malignancy detection in the follow-up of thyroid nodules.


Şişik A, Başak F, Köse E. Tiroid nodüllerine güncel yaklaşım: 2015 ATA ve 2016 AACE/ACE/AME kılavuzları derlemesi. J Arch Clin Exp Med. 2017;2:18-23.

Yassa L, Cibas ES, Benson CB, Frates MC, Doubilet PM, Gawande AA, et al. Long-term assessment of a multidisciplinary approach to thyroid nodule diagnostic evaluation. Cancer. 2007;111:508-16.

Turanli S, Pirhan Y, Ozcelik CK, Cetin A. Predictors of malignancy in patients with a thyroid nodule that contains Hürthle cells. Otolaryngol Head Neck Surg. 2011;144:514-7.

Babajani A, Rahmani S, Raoufi M, Eidgahi ES, Dastjerdi AV, Behfarnia P, et al. Clinico-cytopathological subcategorization in thyroid nodules of atypia of undetermined significance/

Follicular lesion of undetermined significance using the TIRADS and Bethesda classifications. Frontiers in Endocrinology, 2023; 14.1135196

Gharib H, Papini E, Paschke R, Duick DS, Valcavi R, Hegedüs L, et al. AACE/AME/ETA Task Force on Thyroid Nodules. American Association of Clinical Endocrinologists, Associazione Medici Endocrinologi, and European Thyroid Association medical guidelines for clinical practice for the diagnosis and management of thyroid nodules: Executive Summary of recommendations. J Endocrinol Invest. 2010;33:287-91.

Ho AS, Sarti EE, Jain KS, Wang H, Nixon IJ, Shaha AR, et al. Malignancy rate in thyroid nodules classified as Bethesda category III (AUS/FLUS). Thyroid. 2014;24:832-9.

Ozdenkaya Y, Ersavas C, Olmuscelik O, Basim P, Ozover İ, Seker M, et al. Comparison of the Bethesda system classification and postoperative cytology of thyroid nodules: A single center experience. Dicle Tıp Dergisi. 2019;46:443-8.

Kerr L, High-resolution thyroid ultrasound: the value of color Doppler. Ultrasound quarterly. 1994;12:21-44.

Solbiati L, Osti V, Cova L, Tonolini M. Ultrasound of thyroid, parathyroid glands and neck lymph nodes. Eur Radiol. 2001;11:2411-24.

Gezer D, Ecin SM. Tiroid nodüllerinin ultrasonografi, ince iğne aspirasyon ve patolojik olarak karşılaştırması. Balıkesir Medical Journal. 2021;5:140-3.

Ugurluoglu C, Dobur F, Karabagli P, Celik ZE. Fine needle aspiration biopsy of thyroid nodules: cytologic and histopathologic correlation of 1096 patients. Int J Clin Exp Pathol. 2015;8:14800-5.

Bukasa JK, Bayauli-Mwasa P, Mbunga BK, Bangolo A, Kavula W, Mukaya J. The Spectrum of Thyroid Nodules at Kinshasa University Hospital, Democratic Republic of Congo: A Cross-Sectional Study. Int J Environ Res Public Health. 2022;19:16203.

Choi YJ, Jung I, Min SJ, Kim HJ, Kim JH, Kim S, et al. Thyroid nodule with benign cytology: is clinical follow-up enough? PLoS One. 2013;8:e63834.

Miranda-Filho A, Lortet-Tieulent J, Bray F, Cao B, Franceschi S, Vaccarella S, et al. Thyroid cancer incidence trends by histology in 25 countries: a population-based study. Lancet Diabetes Endocrinol. 2021;9:225-34.

Li M, Dal Maso L, Vaccarella S. Global trends in thyroid cancer incidence and the impact of overdiagnosis. Lancet Diabetes Endocrinol. 2020;8:468-470.

Somma J, Schlecht NF, Fink D, Khader SN, Smith RV, Cajigas A. Thyroid fine needle aspiration cytology: follicular lesions and the gray zone. Acta Cytol. 2010;54:123-31.

Crowe A, Linder A, Hameed O, Salih C, Roberson J, Gidley J, et al. The impact of implementation of the Bethesda System for Reporting Thyroid Cytopathology on the quality of reporting, "risk" of malignancy, surgical rate, and rate of frozen sections requested for thyroid lesions. Cancer Cytopathol. 2011;119:315-21.

Ali SZ, Cibas ES. Tiroid Sitopatolojisi Raporlamasında Bethesda Sistemi. Ed: Önder S. 2012:1-167.

Harvey AM, Mody DR, Amrikachi M. Thyroid fine-needle aspiration reporting rates and outcomes before and after Bethesda implementation within a combined academic and community hospital system. Arch Pathol Lab Med. 2013;137:1664-8.

Xie C, Cox P, Taylor N, La Porte S. Ultrasonography of thyroid nodules: a pictorial review. Insights Imaging. 2016;7:77-86.

Anil G, Hegde A, Chong FH. Thyroid nodules: risk stratification for malignancy with ultrasound and guided biopsy. Cancer Imaging. 2011;11:209-23.

Kwak JY, Han KH, Yoon JH, Moon HJ, Son EJ, Park SH, et al. Thyroid imaging reporting and data system for US features of nodules: a step in establishing better stratification of cancer risk. Radiology. 2011;260:892-9.




How to Cite

Özen, F. Z., Keser Şahin, H. H., & Pirhan, Y. (2023). Clinicopathological features and ultrasonographic findings of thyroid nodules classified as atypia of undetermined significance/follicular lesion of undetermined significance : Atypical thyroid nodule findings. The Injector, 2(3), 120–127.