Thyroid Fine-Needle Biopsy: What to Expect

A thyroid fine-needle aspiration biopsy (FNAB) takes a small cell sample from a nodule to determine whether it is benign or malignant. It is the most reliable and least invasive test for this purpose.

Which Nodules Need a Biopsy?

The decision depends on size and ultrasound features (composition, echogenicity, margins, shape, calcifications), summarised in risk systems such as TI-RADS, plus clinical risk factors.

The Procedure

1. You lie on your back with the neck slightly extended.
2. The skin is cleaned and the nodule is located with ultrasound.
3. A needle thinner than a blood-test needle takes 2–4 samples.
4. Pressure is applied and a small plaster placed.

It takes 10–15 minutes and most people describe it as similar to a blood test. Tell your doctor in advance if you take blood thinners — never stop them on your own.

Results (Bethesda System)

Category I non-diagnostic (repeat), II benign (follow-up), III–IV indeterminate (repeat, molecular testing or surgical review), V suspicious and VI malignant (usually surgery). There is no evidence that biopsy spreads cancer.