W. Ouyang1, O. Picado Roque1, S. Liu1, R. Teo1, A. Franco1, M. Gunder1, P. P. Parikh1, J. C. Farrá1, J. I. Lew1 1University Of Miami,Division Of Endocrine Surgery,Miami, FL, USA
Introduction: With the Bethesda System for Reporting Thyroid Cytopathology (BSRTC), thyroid nodules designated as Bethesda Category III or atypia or follicular lesion of undetermined significance (AUS/FLUS) by fine needle aspiration (FNA) have an estimated risk of malignancy (ROM) ranging from 5% to 15%. Previous reports performed at other institutions suggest that the ROM for AUS/FLUS is highly variable. This surgical series determines the ROM and those clinical factors that may predict underlying malignancy in patients with thyroid nodules categorized as AUS/FLUS at a single institution.
Methods: A retrospective review of prospectively collected data of 665 patients with index thyroid nodules who underwent FNA and thyroidectomy from April 2010 to June 2016 was performed. Patients with thyroid nodules classified as AUS/FLUS by FNA were divided into malignant or benign groups based on final pathology, noting whether malignancy was found in the index thyroid nodule or as an incidental lesion. Incidental cancers were defined as malignancy discovered outside the index nodule within the ipsilateral thyroid lobe or contralateral lobe. Such patients underwent initial thyroid lobectomy for definitive diagnosis unless there was a history of radiation exposure, familial thyroid cancer, obstructive symptoms, bilateral nodules and/or patient preference for which total thyroidectomy was performed. Groups were compared in terms of demographics, clinicopathologic factors, and surgeon performed ultrasound (SUS) features for malignancy.
Results: Among the 171 patients with AUS/FLUS nodules who underwent thyroidectomy, final pathology confirmed malignancy in 60% (103/171) of the patients compared to benign disease in 40% (68/171). Malignancy in the index thyroid nodule alone was found in 37% (64/171) of patients whereas incidental cancers were found in 9% (16/171) on final pathology. Twenty-three (14%, 23/171) patients were found to have both index nodule and incidental malignancy. The ROM for index thyroid nodule with AUS/FLUS overall is 51% (87/171). Papillary thyroid cancer (PTC) was the most common cancer, found in 86% (89/103) of patients with malignancy. The most common subtype among patients with PTC was the follicular variant in 71% (63/89), followed by the classic variant in 12% (11/89). Analysis of nodule features by SUS revealed solid texture more likely to be present in patients with a malignancy when compared to benign tumors (88.1% vs 73.5%, p<0.05).
Conclusion: In this surgical series, the malignancy rate of 51% in thyroid nodules with AUS/FLUS cytology is higher than the estimated ROM, but within range of other surgical reports in the literature. Furthermore, during SUS evaluation, solid features may help determine underlying malignancy in AUS/FLUS thyroid nodules. For appropriate treatment recommendations, surgeons should assess their ROM for AUS/FLUS nodules, which may vary in their everyday clinic practice and local institutional experience.