Circulating microRNA-222 and microRNA-146b: a potential differentiating tool between benign and malignant thyroid...

Thyroid nodules are common, and the majority are of benign nature, however the main clinical aim remains to discriminate malignant ones. Despite that, the actual routine workup for thyroid nodules including hormonal testing, ultrasound scan, scintigraphy, and Fine needle aspiration cytology (FNAC) is still deficient, often necessitating surgical intervention for a conclusive histopathological examination and diagnosis. Therefore, searching for molecular tools that help in differentiating benign and malignant thyroid nodules gains an increasing interest.

This case-control study was conducted on 46 adults, categorized into two groups (23 patients each) one with benign and another with malignant thyroid nodules, based on post- operative histopathology. Prior to surgery patients have undergone clinical examination and ultrasonography (US) neck and only patients with US - TIRADs 3, 4 and 5 thyroid lesions were referred for FNAC and included in this study. Surgery decisions were made according to FNAC Bethesda classification. Total RNA was extracted from plasma samples prior to surgery. The reverse transcription of miRNA to cDNA was followed by Real Time PCR Amplification in triplet to analyze miRNA-222, miRNA-146b and reference miRNA-16. Plasma from 40 healthy subjects was used as control for the calculations of the relative expression of miRNA using RT-qPCR.

The results showed a statistically significant increased expression of plasma miRNA-222 and miRNA-146b in the malignant nodules group than benign group (p = 0.001 and p= <0.001, respectively). Also, there is a statistically significant difference between benign and malignant groups regarding the presence of plasma miRNA-222 or plasma miRNA-146b with higher levels than Youden Index cutoffs (p= <0.001). MiRNA-222 showed increased plasma expression with vascular invasion of malignant nodules. Adding the estimation of plasma miRNA-222 and 146b levels to the actual ultrasound features and to FNAC Bethesda classification, raised AUC of ROC of the mentioned tools for the diagnosis of malignant thyroid nodules.

These findings suggest a potential role for miRNA-222 and miRNA-146b in differentiating benign and malignant thyroid nodules and may provide a valuable diagnostic addition to the current routine workup.