Molecular Analysis Based on Fine-Needle Aspiration Washout Samples in Thyroid Nodules

Area of Science:

• Endocrinology
• Molecular Diagnostics
• Surgical Pathology

Background:

• Molecular testing refines risk stratification for indeterminate thyroid nodules (Bethesda III-IV).
• Limited data exist on dual-gene (BRAF and RAS) testing using fresh fine-needle aspiration (FNA) washout specimens.

Purpose of the Study:

• To evaluate the performance of BRAF and RAS mutation analysis from fresh thyroid FNA washout material.
• To focus on indeterminate thyroid cytology for improved diagnostic accuracy.

Main Methods:

• Retrospective analysis of 1139 patients undergoing washout-based molecular testing.
• Assessment of sample adequacy, mutation spectrum, and diagnostic metrics (sensitivity, specificity, PPV, NPV, accuracy).
• Analysis within the Bethesda III-IV subset and under different classification assumptions for borderline lesions.

Main Results:

• Adequate material for molecular analysis was obtained in 90.9% of samples.
• In operated patients (n=307), malignancy was present in 31.9%.
• For indeterminate nodules, dual-gene testing showed sensitivity of 48.0%, specificity of 89.6%, and accuracy of 72.9% when borderline lesions were classified as benign.

Conclusions:

• Dual-gene (BRAF and RAS) testing from fresh FNA washouts is technically feasible with high sample adequacy (≥90%).
• This method provides high specificity and modest sensitivity for malignancy in indeterminate thyroid nodules.
• It serves as a practical, low-complexity adjunct to cytology and imaging for preoperative decision-making, especially where comprehensive panels are unavailable.