Abstract
The management of thyroid nodules of indeterminate cytology is controversial. Our study aimed to establish the frequency and significance of H-,K-,N-RAS, TERT promoter, and BRAF gene mutations in thyroid nodes of indeterminate cytology and to assess their potential usefulness in clinical practice. H-,K-,N-RAS, TERT promoter and BRAF gene mutations were examined in a series of 199 consecutive nodes of indeterminate cytology referred for surgical excision. 69/199 (35%) were malignant on histopathological review. RAS mutations were detected in 36/199 (18%), and 19/36 cases (53%) were malignant on histological diagnosis. TERT promoter mutations were detected in 7/199 (4%) nodules, which were all malignant lesions. BRAF mutations were detected in 15/199 (8%), and a BRAF K601E mutation was identified in 2 follicular adenomas and 1 noninvasive follicular thyroid neoplasm with papillary-like nuclear features. Altogether, this panel was able to identify 48% of the malignant lesions, achieving a specificity, positive predictive value, and negative predictive value for malignancy of 85, 62, and 75%, respectively. The residual malignancy risk in mutation-negative nodes is 25%. These nodes still need to be resected, but mutation analysis could help to orient the appropriate surgical strategy.
Highlights
Fine-needle aspiration (FNA) cytology is the gold standard for the nonsurgical assessment of thyroid nodules, but it is unable to exclude cancer in one in four cases, which are labeled as “indeterminate” [1]
The study involved 199 FNA samples of indeterminate cytology obtained from thyroid nodules in 199 consecutive patients referred for surgical excision from December 2012 to May 2016
In the group of 111 patients classified according to the SIAPEC 2014 system, 63 were TIR 3A and 48 were TIR 3B
Summary
Fine-needle aspiration (FNA) cytology is the gold standard for the nonsurgical assessment of thyroid nodules, but it is unable to exclude cancer in one in four cases, which are labeled as “indeterminate” [1]. Indeterminate lesions are separated into TIR 3A and TIR 3B, with an estimated malignancy risk below 10% for the former, and around 15–30% for the latter. Reference might be made to the malignancy risk of the extensively studied Bethesda classification. Atypia and follicular lesions of undetermined significance (AUS/FLUS) includes cytological/nuclear atypia in the Bethesda system, which would convert a TIR 3A into a TIR 3B in the SIAPEC system [5]. Such an unclear picture sometimes makes it difficult to manage patients with thyroid nodules of indeterminate cytology and to choose between surveillance and diagnostic surgery. A more accurate preoperative diagnosis of cancer in thyroid nodules would enable such unnecessary or two-step surgery to be avoided
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