Description:
<jats:sec><jats:title>Background</jats:title><jats:p>Activating point mutations of the <jats:italic>RAS</jats:italic> gene (<jats:italic>NRAS</jats:italic>, <jats:italic>HRAS</jats:italic>, and <jats:italic>KRAS</jats:italic>) can be seen in benign and malignant thyroid tumors; among these, <jats:italic>NRAS</jats:italic> mutations are more commonly seen. This study was conducted to evaluate the thyroid risk of malignancy (ROM) associated with <jats:italic>RAS</jats:italic> mutations in thyroid fine‐needle aspiration (FNA) at the authors' institution.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>The authors searched their electronic database system between January 2015 and May 2021 for thyroid FNA cases with any type of <jats:italic>RAS</jats:italic> mutation. Molecular alterations were identified with the ThyroSeq Genomic Classifier, ThyGeNEXT (thyroid oncogene panel)/ThyraMIR (miRNA classifier), or ThyroSure gene panel.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>A total of 127 cases (age, 51 ± 14 years; 100 females and 27 males) were identified, and 72 had histologic follow‐up. The overall ROM associated with <jats:italic>RAS</jats:italic> mutations (with or without any other molecular alterations) was 29%, whereas the ROM was lower (18%) with <jats:italic>RAS</jats:italic> mutations only. Isolated <jats:italic>NRAS</jats:italic>, <jats:italic>HRAS</jats:italic>, and <jats:italic>KRAS</jats:italic> mutation–associated ROMs were 15%, 27%, and 14%, respectively. Among these <jats:italic>RAS</jats:italic>‐mutated cases, the cases with a Bethesda category IV cytologic diagnosis had a higher ROM than the cases with a category III diagnosis (38% vs 17%). Twenty‐one histologically confirmed malignant cases were mostly classified on cytology as category IV lesions (14 of 34; 41%), and the remainder were either category III (6 of 35; 17%) or V lesions (1 of 1; 100%).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>This study demonstrated that the overall <jats:italic>RAS</jats:italic> mutation–associated ROM in thyroid FNA was intermediate (29%), and isolated <jats:italic>HRAS</jats:italic> mutations appeared to have a higher ROM (27%) than <jats:italic>NRAS</jats:italic> and <jats:italic>KRAS</jats:italic> mutations (15% and 14%, respectively).</jats:p></jats:sec>