Clinicopathologic Determinants of Thyroid Fine-Needle Aspiration Specimens Diagnosed as Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance

Abstract

The diagnostic category of atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) in The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) has proven to be heterogeneous in terms of usage and clinical outcome. Several factors have been noted in the literature to lead to AUS/FLUS diagnosis. In this study, we assessed the significance of various clinicopathologic factors that may influence AUS/FLUS diagnosis. A search of our laboratory information system was performed to identify all in-house thyroid fine-needle aspiration (FNA) cases performed under ultrasound (US) guidance and diagnosed as AUS/FLUS from 2008-2011. Data-points collected for this study included: patient demographic information, size of the thyroid nodule sampled, aspirator, pathologist rendering the final diagnosis, and applicable follow up. The case cohort included 348 cases diagnosed as AUS/FLUS in 87 males and 261 females (average age of 56 years). All FNAs were performed under ultrasound guidance; 171 (49%) nodules were aspirated by a team of endocrinologists and 177 (51%) by a team of radiologists. The nodule size was available in 328 cases (average size of 2.63 cm); 14 (4%) measured <1.0 cm, 217 (66%) were 1.1-3.0 cm and 97 (30%) were 3.1->4.1 cm. Five cytopathologists interpreted all thyroid FNA cases; the AUS/FLUS rate varied from 10.2% in 2009 to 8% in 2011. Of the 348 cases diagnosed as AUS/FLUS, 219 (63%) were interpreted by two and the remaining 129 (37%) by three cytopathologists. Follow-up was available in 260 (75%) cases; 187 (54%) had 1-3 repeat FNA procedures. Histologic follow-up was available in 139 (40%) cases with an overall malignancy rate of 32% (45 cases). The malignancy rate was highest (32%) in nodules measuring 2.1-3.0 cm. Based on this study cytopathologic interpretation is the most significant factor for the variable rate and follow-up of cases diagnosed as AUS/FLUS.

Implications of a suspicious afirma test result in thyroid fine‐needle aspiration cytology: An institutional experience

“…As mentioned earlier, Afirma analysis in the study institution is mainly performed on repeat AUS/FLUS cases. The incidence of malignancy at the time of thyroidectomy in cases diagnosed as AUS/FLUS on repeat FNA, but on which Afirma testing has not been performed, is 39.4% . From this data, it is evident that cases diagnosed as AUS/FLUS on repeat FNA have a significantly higher incidence of malignancy than those diagnosed as AUS/FLUS on first FNA.…”