Aims Analysis of molecular markers in addition to cytological analysis of fine-needle aspiration (FNA) samples is a promising way to improve the preoperative diagnosis of thyroid nodules. Previously, we have developed an algorithm for the differential diagnosis of thyroid nodules by means of a small set of molecular markers. Here, we aimed to validate this approach using FNA cytology samples of Bethesda categories III and IV, in which preoperative detection of malignancy by cytological analysis is impossible.
Methods A total of 122 FNA smears from patients with indeterminate cytology (Bethesda III: 13 patients, Bethesda IV: 109 patients) were analysed by real-time PCR regarding the preselected set of molecular markers (the BRAF V600E mutation, normalised concentrations of HMGA2 mRNA, 3 microRNAs, and the mitochondrial/nuclear DNA ratio). The decision tree–based classifier was used to discriminate between benign and malignant tumours.
Results The molecular testing detected malignancy in FNA smears of indeterminate cytology with 89.2% sensitivity, 84.6% positive predictive value, 92.9% specificity and 95.2% negative predictive value; these characteristics are comparable with those of more complicated commercial tests. Residual risk of malignancy for the thyroid nodules that were shown to be benign by this molecular method did not exceed the reported risk of malignancy for Bethesda II histological diagnosis. Analytical-accuracy assessment revealed required nucleic-acid input of ≥5 ng.
Conclusions The study shows feasibility of preoperative differential diagnosis of thyroid nodules of indeterminate cytology using a small panel of molecular markers of different types by a simple PCR-based method using stained FNA smears.
- thyroid cancer
- molecular oncology
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Handling editor Runjan Chetty.
Contributors ST and MKI were involved in the study conception; ST and YAV conceived and designed the experiments; SAL, SVS and GAK collected the samples from patients; YAV conducted the experiments; ST and PSD participated in the data analysis and interpretation; ST and SAL wrote the manuscript; MKI, PSD and SVS revised the manuscript.
Funding The work was supported by Russian state budget projects No. 0324-2019-0040-C-01 and 0310-2019-0013. The funding body was not involved in the study design, data acquisition, interpretation of the results or writing of the manuscript.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The study protocol was approved by the ethics committee of the South Ural State Medical University.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.