Incidence and Predictive Factors of Inadequate Fine-Needle Aspirates for BRAFV600E Mutation Analysis in Thyroid Nodules

Abstract

BRAF(V600E) mutation (valine-to-glutamate substitution at residue 600 of the B-type Raf kinase gene) analysis from thyroid aspirates is increasingly used as a prognostic or diagnostic marker. However, it is limited under some conditions. The purpose of this study was to assess the incidence and predictive factors of thyroid nodules with specimens inadequate for BRAF(V600E) mutation analysis. We performed a retrospective cohort study of consecutive patients who underwent ultrasound-guided fine-needle aspiration (FNA) and molecular testing of aspiration specimens. Patients who had inadequate specimens in both allele-specific polymerase chain reaction and direct DNA-sequencing methods were selected. Univariate and multivariate logistic regression analyses were performed to identify predictive factors of specimens inadequate for molecular tests. Specimens inadequate for BRAF(V600E) mutation analysis were seen in 168 of 7001 (2.4%) patients. Factors, including patient age and sex, nodule size, ultrasound diagnosis, the presence of calcification, and cystic changes within thyroid nodules, were not significant predictors of inadequate mutation analysis. Oval-to-round or irregular shapes (e.g., not taller-than-wide) and final benign results were significant factors in univariate analysis (p = 0.0002 and p = 0.0013, respectively). However, nodules aspirated by operators with less than 1 year of experience (odds ratio [OR], 3.005; p = 0.0070), and those that had spiculated margins (OR, 6.139; p = 0.0142), isoechogenicity (OR, 10.374; p = 0.0442), or nondiagnostic cytologic findings (OR, 73.637; p = 0.0055) remained significant risk factors after adjustment in multivariable analysis. Thyroid nodule specimens inadequate for BRAF(V600E) mutation analysis were frequently associated with FNA aspiration performed by inexperienced operators, nondiagnostic cytologic findings, benign nodules on final diagnosis, and probably benign ultrasound findings, such as isoechogenicity and not-taller-than-wide shape.