FNA biopsy

Fine needle aspiration (FNA) biopsy is a straightforward outpatient procedure used to take a small sample of cells from a thyroid nodule. The sample is examined under a microscope by a pathologist to determine whether the cells look benign, suspicious, or malignant.

A thin needle is inserted into the nodule - usually under ultrasound guidance to ensure accurate placement - and cells are drawn up by gentle suction. The procedure typically takes a few minutes. Local anaesthetic is sometimes used, though many patients find the discomfort mild. Afterwards, there may be slight bruising or tenderness at the site.

In the UK, FNA results are classified using the Royal College of Pathologists (RCPath) 'Thy' reporting system (Thy1 to Thy5), which grades samples from non-diagnostic through benign to malignant. This aligns with the international Bethesda system. The result, combined with ultrasound features and clinical factors, guides decisions about monitoring or surgery.

FNA does not diagnose every thyroid cancer - some nodules are indeterminate on biopsy, and occasionally a second biopsy or diagnostic surgery is needed. Speak to your specialist about what a result means in your individual case.