The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has been used by pathologists since 2010, providing a standardized language, updated in 2017 and finally in 2023. According to the latest update, category III has been divided into two subgroups: " Atypia of uncertain significance (AUS) -nuclear atypia" and "AUS-other." We aimed to analyze the risk of malignancy in patients diagnosed with category III (AUS, follicular lesion of uncertain significance (FLUS), or AUS/FLUS) and compare them based on recent changes in cytologic-histopathologic correlation. We retrospectively evaluated thyroid fine needle aspiration materials diagnosed as category III. We categorized the cases as AUS, FLUS, or AUS/FLUS. The cytopathologic and histopathologic diagnoses in the resection materials were then compared. Based on detailed microscopic descriptions in our reports, we reclassified the cases as "AUS-nuclear atypia" and "AUS-other" according to the updated 2023 TBSRTC.Our study included 73 patients, who had undergone thyroidectomy. Of these, 45.21% were reported as FLUS, 47.94% as AUS, and 6.85% as AUS/FLUS in thyroid cytology. Surgical follow-up showed no significant differences in malignancy risk, both between the FLUS and AUS groups (p=.232) and between cases diagnosed as "AUS-nuclear atypia" and "AUS-other" (p=.826). Within the indeterminate group, category III has the lowest risk of malignancy, with a predicted risk between 10-30%. However, since this group is heterogeneous, the reported malignancy risk in the literature ranges from 6-72.9%, depending on the type of atypia leading to the AUS interpretation. According to the literature, it was reported that the subgroup exhibiting the highest nuclear atypia had the highest risk of malignancy.
Key words: Thyroid, cytology, category III, fine needle aspiration
|
