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.


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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.



Original Article