Endocrine Abstracts

Introduction: 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.

Methods: From 1529 patients with 1838 thyroid nodules, 11.4% of the nodules was diagnosed as AUS/FLUS. From 111 patients with FLUS, we analyzed 95, 88 females and seven males.

Results: 26 patients (27.4%) had directly undergone to neck surgery and five (19.2%) had malignant nodules. 51 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 who were submitted to a second FNAC, 12 undergone to surgery and two nodules were malignant. 18 patients (18.9%) kept 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 FLUS, 38 (40%) were submitted to neck surgery and seven 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. The malignancy rate was 16.7% in patients who repeated FNAC and 19.2% in patients who undergone directly to surgery.

Conclusion: 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 BRAF mutation testing could help in this decision.