Thyroid puncture: what is it for and how to understand the result

Fine-needle aspiration puncture - PAAF of the thyroid is the best test to determine whether a thyroid nodule is benign or malignant, which is essential information to determine the type of treatment to be performed next.

Normally, small and benign thyroid nodules do not need treatment, but in case of large nodules, even if benign, surgery may be necessary for their removal, and in the case of a malignant nodule, the thyroid should always be removed, because it represents a cancer. Learn how to identify a lump in the thyroid.

When PAAF is requested

The doctor orders a Fine Needle Aspiration Puncture when the ultrasound exam shows:

  • Thyroid nodule of more than 0.5 cm and less than 1 cm, suspected of being malignant;
  • All nodules larger than 1 cm, being hypoechoic, complex or spongiform;
  • When there is a first-degree relative with thyroid cancer;
  • When the person was exposed to radiation in childhood or adolescence;
  • Nodule with apparent invasion outside the thyroid;
  • In case of suspected lymph node during ultrasound.

When there is more than one nodule in the thyroid, all of them must be examined, removing solid and liquid parts from all of them to be analyzed in the laboratory.

How PAAF is made

The Fine Needle Aspiration Puncture can be done at the same time as the thyroid ultrasound, with a better result, or just with the palpation of the nodule. When the FNAB is performed, small pieces of tissue that make up the nodule are removed so that it can be analyzed in the laboratory, and during this examination the liquid part can also be removed to be analyzed and to reduce the size of the nodule.

PAAF hurts a little but the pain is bearable, and the person leaves the test with only a band-aid covering the puncture site. It is not possible to perform this exam under anesthesia, because the only anesthesia that would be effective is general anesthesia, whose risks do not justify its performance during this exam.

People taking anticoagulant medications such as AAS, heparin or warfarin, should stop taking these medications for 3 days before performing this puncture.

Know the tests that evaluate the thyroid.

Understanding the results

The results of Fine Needle Aspiration Puncture, according to the classification of the Bethesda System, may indicate:

CategoryWhat does it meanRecommendation
Category I:Non-diagnostic, unsatisfactory sampleRepeat PAAF with ultrasound
Category II:Benign nodule: colloid goiter, hyperplastic nodule or lymphocytic thyroiditisat medical discretion
Category III:

Atypias, follicular lesion of undetermined meaning, that is, inconclusive

Repeat the FNAP in 3 months and consider surgery
Category IV:Suspected for follicular neoplasia or follicular neoplasia, that is, inconclusivePonder the surgery
Category V:Suspicious for malignancySurgery indicated to remove only 1 lobe or total thyroid removal
Category VI:MalignantRecommended to remove the thyroid with surgery


These are recommendations only, so endocrinologists or head and neck surgeons can decide if there is a need to repeat the test between 3 to 6 months to compare the results and assess whether the nodule has grown, for example, and then decide whether it is I need to perform surgery to remove the thyroid and perform treatment with Radioactive Iodine, if applicable.

Where to do and price

PAAF can be performed in imaging laboratories, clinics and hospitals. The price of this exam varies between 700 to 1500 reais, but it can be done by SUS or by the private health plan, in some places, when the exam needs to be repeated in 3 months, no new payment is necessary, but it is important to confirm this information before to take the exam.