The impact of repeat fine‐needle aspiration in thyroid nodules categorized as atypia of undetermined significance or follicular lesion of undetermined significance: A single center experience

Abstract

Background Atypia of undetermined significance (AUS) or follicular lesion of undetermined significance (FLUS) is the most controversial category of the Bethesda System. The present study was conducted to compare the histological findings in a series of thyroid nodules diagnosed with AUS/FLUS after single or repeat fine needle aspiration (FNA) cytology. Methods Retrospective analysis of our institution's series of 514 patients with an initial diagnosis of AUS/FLUS between 11/2011 and 02/2020. Results Of 4887 FNA samples, 11.8% were classified as AUS/FLUS. Of patients with an initial AUS/FLUS diagnosis, 11.5% (59/514) underwent surgery after a single FNA, 55.4% (285/514) had a repeat FNA, and 32.7% (168/514) were either observed or lost to follow‐up. Surgical pathology was available in 123 cases (23.9%), and malignancy was confirmed in 32.5% (40/123) cases, with similar rates in the single 32.2% (19/59) and repeat FNA 32.8% (21/64) groups. Repeat FNA reclassified 78.9% of the AUS/FLUS cases to a different category: 57.2% were reclassified as benign, 10.5% as follicular neoplasm, and 5.6% as suspicious for malignancy or malignant. The rates of nonneoplastic benign lesions were 52.5% (31/59) and 31.2% (20/64) in the single and repeat FNA groups, respectively (P = .018). The rates of follicular adenomas were higher when repeat FNA was performed (23/64, 35.9%) compared with a single FNA (9/59; 15.2%) (P = .013). Conclusion In this series, a repeat FNA in cases of AUS/FLUS increased detection of follicular adenomas but not the detection of malignancy. Repeat FNA reduced the rate of benign nonneoplastic lesions by 40% in the surgical samples.

Malignancy outcomes and the impact of repeat fine needle aspiration of thyroid nodules with Bethesda category III cytology: A multicenter experience

“…6,10 Malignancy rates above 30% were frequently reported in recent studies. 7,11 Moreover, higher frequency values like 52.5% and 55.5% were detected in other studies. 12,13 We showed -similar to the aforementioned articles-that the malignancy rate is higher than it was traditionally considered.…”

“…Overestimated malignancy rates may be calculated because of the bias for surgical candidate selection. 7 Clinical and ultrasonographic features, patients' preference for treatment and the experience of the medical center affect the patient selection for surgery. As a result, different malignancy rates were calculated in different studies.…”

“…4,5 But further studies showed higher rates of malignancy for category III and a recent meta-analysis showed a high rate of 27.4% malignancy. 6,7 This raised concerns that the malignancy risk for Bethesda category III is higher than it was traditionally believed.…”

Atypia and Follicular Lesions of Undetermined Significance in Subsequent Biopsy Result: What Clinicians Need to Know

“…They propose management options for nodules such as observation, surgery, or repeat UG-FNAB. Marin et al [ 9 ] suggest that repeat UG-FNAB in cases of AUS/FLUS category increases detection of follicular adenomas. Focal or extensive but mild cytological and architectural atypia are insufficient to be assigned to a higher category, and atypia in follicular/lymphoid cells is classified as category III of TBSRTC [ 3 ].…”

“…Thus, AUS and FLUS do not provide a differential diagnosis between malignant and benign lesions. Some authors admit that it is the most controversial category of this classification [ 9 ]. The occurrence of two or more subsequent biopsy results with AUS/FLUS diagnosis makes these clinical situations even more complex.…”