Follow up of follicular lesion of undetermined significance in thyroid nodulesfine needle aspiration cytology

The Atypia of Undetermined Significance/Follicular lesion of Undetermined Significance (AUS/FLUS) category of the Bethesda Classification for thyroid nodules fine needle aspiration cytology (FNAC) is reserved for specimens that contain cells with architectural and/or nuclear atypia that is not sufficient to be classified as suspicious or malignant. Our objective is to report our experience in the follow-up and outcome of patients with AUS/FLUS in thyroid nodules FNAC. From 1529 patients with 1838 thyroid nodules, 11,4% of the nodules were diagnosed as AUS/FLUS. From 111 patients with AUS/FLUS, we analyzed 95, 88 females and 7 males. Twenty-six patients (27.4%) had directly neck surgery and five (19.2%) had malignant nodules. Fifty-one patients (53.7%) repeated FNAC. On the second FNAC, 17 (33.3%) nodules were benign, 22 (43.1%) were AUS/FLUS, 11 (21.6%) were non-diagnostic and 1 (1.9%) was malignant. From the patients submitted to a second FNAC, 12 undergone to surgery: eight with AUS/FLUS, two non-diagnostic, one benign and one malignant. The histology revealed that two nodules were malignant. Eighteen patients (18.9%) did only clinical follow up without repeating FNAC or surgery. Six patients (6.3%) repeated FNAC a third time: four nodules were benign and two non-diagnostic. Among the 95 patients with AUS/FLUS, 38 (40%) were submitted to neck surgery and seven (18.4%) had a malignant diagnosis. The malignancy rate in the 95 patients with AUS/FLUS was 7.4%, but 18.4% in the patients who did surgery. In this category the recommendation is to repeat the FNAC rather than excision. We suggest the follow up of these patients should be individualized and discussed in multidisciplinary teams. The combination of clinical suspicion, ultrasound characteristics and molecular tests could help in this decision. (C) 2015 Sociedade Portuguesa de Endocrinologia, Diabetes e Metabolismo. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).