Outcomes of Bethesda categories III and IV thyroid nodules over 5 years and performance of the Afirma gene expression classifier: A single‐institution study

• Published in: Clinical endocrinology (Oxford) 2018-08, Vol.89 (2), p.226-232
• Main Authors: Deaver, Kelsi E., Haugen, Bryan R., Pozdeyev, Nikita, Marshall, Carrie B.
• Format: Article
• Language: English
• Subjects: atypia of undetermined significance; Benign; Bethesda; Cytology; Gene expression; gene expression classifier; indeterminate thyroid cytology; Malignancy; molecular marker; Nodules; Surgery; suspicious for follicular neoplasm; Thyroid; Thyroid cancer; Thyroid gland
• ISSN: 0300-0664; 1365-2265
• DOI: 10.1111/cen.13747

Summary Objective The second edition Bethesda System for Reporting Thyroid Cytology estimates 6%‐18% malignancy rate of category III (B3) and 10%‐40% for category IV (B4) nodules; however, reported malignancy rates have considerable variability among institutions. Use of molecular classifiers (including Afirma Gene Expression Classifier, GEC) can be utilized in management of thyroid nodules. Our objective was to analyse malignancy rates of B3 and B4 nodules and determine clinical outcomes of GEC Benign nodules. Methods A retrospective analysis of 2019 thyroid FNAs was performed at the University of Colorado from 2011 to 2015, including molecular, surgical and clinical follow‐up. Results Of 2019 FNAs analysed, 231 (11.4%) were diagnosed as B3 and 80 (4.0%) as B4. GEC was obtained in 54.1% of B3 cases, with nearly half (48.8%) having a Benign result. Surgery was performed in 40.7% B3 cases with a 24.5% malignancy rate, ranging 8%‐38% by year. In the B4 group, 52.5% underwent molecular testing with 28.6% as GEC Benign. About 68.8% of B4 cases underwent surgery with a 20% malignancy rate, ranging 0%‐42% by year. Seventy‐three GEC Benign cases were reviewed: 5 (6.8%) underwent surgery, with none demonstrating malignancy in the target nodule. Size remained stable for most GEC Benign nodules: 75.9% (B3) and 71.4% (B4) with no malignancy on repeat FNA. Conclusions Our 5‐year review demonstrated that malignancy rates of B3 and B4 nodules showed year‐to‐year variability. We suggest that clinicians use a multi‐year average of their institution's malignancy rates to optimally manage patients. Follow‐up for GEC Benign cases thus far supports their indolent nature.