Ultrasound-guided fine needle aspiration (FNA) is a diagnostic procedure that assists doctors in diagnosing various thyroid lesions. During the examination, you simply lie on the examination table, and the doctor uses ultrasound for localization to determine the exact position of the thyroid lesion. They then use a fine needle (usually a 21G or 23G needle) to extract an adequate sample of cells from the thyroid lesion. The examination generally takes about ten minutes.

The extracted cells are sent to the pathology department for laboratory analysis. The doctor carefully examines the cells under a microscope, observing their morphology, activity, invasiveness, and other characteristics to make a diagnosis.

This examination can help doctors differentiate between benign and malignant thyroid lesions, as well as determine the nature of the lesion.