Cytological features and nuclear scores: Diagnostic tools in preoperative fine needle aspiration of indeterminate thyroid nodules with RAS or BRAF K601E mutations?

INTRODUCTION: The cytological diagnosis of follicular-patterned thyroid lesions is challenging, especially since the World Health Organisation classification has recognised non-invasive follicular thyroid neoplasm with papillary-like features. These entities are often classified as indeterminate on cytology. Molecular testing has been proposed to help classify indeterminate nodules. RAS and K601E BRAF mutations are mostly encountered in follicular-patterned lesions, but their diagnostic value is not well established. Nuclear scores have also been proposed to help classify indeterminate lesions. OBJECTIVE: To investigate the correlation between cytological features and histology and to assess nuclear scores in a series of indeterminate RAS or BRAF K601E positive thyroid nodules. METHODS: The cytological parameters of 69 indeterminate RAS or BRAF K601E-positive thyroid nodules were evaluated. The Strickland and Maletta scores and a new nuclear score were assessed. Diagnosis of malignant, benign or indolent neoplasms was confirmed in each case by histology. Malignant and indolent nodules were considered surgical nodules, and adenomas non-surgical nodule. RESULTS: Surgical nodules were associated with the presence of ground glass nuclei (P = .001), grooves (P < .001) or irregular nuclear membranes (P = .01) on cytology. Nuclear scores were more often ≥2 in surgical nodules compared to benign ones (P < .001), with high sensitivity, but a low negative predictive value. CONCLUSIONS: Analysis of nuclear features is useful to distinguish non-surgical from surgical nodules in indeterminate FNAs. Although nuclear scores are not ideal rule-out tests for indeterminate RAS or BRAF K601E positive nodules, they seem useful to screen non-molecular tested or non-mutated indeterminate FNAs. This work shows that meticulous analysis of nuclear features on cytological specimens can be useful to distinguish non-surgical nodules (adenoma) from surgical nodules in indeterminate FNAs. Although nuclear scores are not rule-out tests for indeterminate RAS or BRAF K601E positive nodules, they are useful in screening non-molecular tested or non-mutated indeterminate FNAs for surgery.

Feasibility and performance of the Idylla™ NRAS/BRAF cartridge mutation assay on thyroid liquid-based fine-needle aspiration.

BACKGROUND: Thyroid nodules with indeterminate cytology represent up to 30% of cases. Molecular testing is now highly recommended to improve management. This study aimed to evaluate the use of the Idylla™ NRAS/BRAF mutation test, a rapid and automated polymerase chain reaction (PCR) assay validated for fixed paraffin-embedded use, on residual thyroid liquid-based fine-needle aspiration (LB-FNA). METHODS: Concordance between mutations detected by the Idylla™ assay and the gold-standard qPCR was assessed by splitting in two aliquots 31 BRAF or RAS mutated and 5 non-mutated LB-FNA samples. Samples were obtained either from simulated FNA after thyroidectomy or from FNA obtained during routine care. A third aliquot was used to assess the limit of detection of Idylla™ for five mutated samples. RESULTS: The Idylla™ assay showed a sensitivity of 97% and a specificity of 83% as results were concordant for 34 out of 36 samples. One discordant sample concerned a BRAF p.K601E-mutation which is not detected by the Idylla™ cartridge. The other showed a false-positive NRAS p.A146T detection and a weak BRAF p.V600E detection. The limit of detection of the Idylla™ assay was not reached by the dilution assay. CONCLUSION: Idylla™ NRAS/BRAF mutation testing can be performed on residual thyroid LB-FNA, using low DNA quantity input, thus not requiring a dedicated sample. The Idylla™ NRAS/BRAF assay offers a quick and easy first step for analyzing the main molecular alterations in indeterminate thyroid nodules, hence improving diagnostic management.

Thyroglobulin measurement in fine-needle aspirates of lymph nodes in patients with differentiated thyroid cancer: a simple definition of the threshold value, with emphasis on potential pitfalls of the method.

BACKGROUND: Thyroglobulin measurements in fine-needle aspirate (FNA-Tg) is an accurate method for the diagnosis of lymph node metastasis in differentiated thyroid carcinoma. The goal of this study is to determine the most appropriate diagnostic threshold value for FNA-Tg. METHODS: Ultrasound-guided fine-needle aspiration-cytology (FNA-C) and FNA-Tg were performed on suspicious lymph nodes in 114 consecutive patients with thyroid cancer prior to thyroidectomy (n=13) or during follow-up (n=93), and in 16 control subjects. Functional sensitivity of the thyroglobulin assay was 0.7 ng/mL. Sensitivity and specificity of FNA-Tg and FNA-C were determined for different cut-off values within a range of 0.69-1.34 nanogram/punction (ng/p) using receiver operating characteristic curve analysis. RESULTS: The FNA-Tg cut-off value of 0.93 ng/p offers the best diagnostic performances: 94.2% sensitivity, 97.8% specificity. FNA-C showed 100% specificity in diagnostic samples, but low sensitivity of 71% due primarily to inadequate samples. Combining FNA-C and FNA-Tg resulted in 98% sensitivity and 100% specificity. CONCLUSIONS: A unique threshold of 0.93 ng/p gives high sensitivity and specificity, even in non-thyroidectomized patients. However, since false negative results may be observed in poorly differentiated thyroid cancer, FNA-C should remain combined to FNA-Tg.