Fine Needle Puncture and Aspiration (FNA) in thyroid pathology: what is it and what is it for

Dr. Tébar is a prestigious specialist in Endocrinology and an important scientific disseminator. In the following article he explains the uses and utilities of Fine Needle Puncture and Aspiration (FNA) for thyroid pathologies.

How can we classify thyroid pathology?

The pathology of the thyroid gland can be classified into:

1. Dysfunctional: hypothyroidism and hyperthyroidism.
2. Inflammatory: the different types of thyroiditis (acute, subacute and chronic).
3. Tumoral: cysts, adenomas or benign tumors and carcinomas or malignant tumors. Thyroid pathology can be divided into familial (affecting several members of the same family) or isolated.

Most important diagnostic methods in thyroid pathology

In dysfunctional pathology, the determination of thyroid hormones and TSH is usually sufficient, although sometimes the analysis of antithyroid antibodies or anti-TSH receptor antibodies is necessary. In inflammatory thyroid disease, if there is a phlegmon or abscess, bacterial cultures are sometimes necessary; in subacute thyroid disease, a very important finding is a very high ESR or a white scintigraphy; in chronic thyroid disease, if it is Hashimoto’s disease, the most diagnostic tests are anti-TPO antibodies and ultrasound; Riedel’s disease is very rare and is diagnosed by manual exploration of the gland due to its irregularity, adhesion to neighboring tissues and hardness. In tumor pathology, ultrasound and ultrasound-guided FNA are undoubtedly the diagnostic tools par excellence. There are other very modern means such as genetic studies or elastography, which are increasingly used.

What is Fine Needle Puncture and Aspiration (FNA) and what is it used for?

Fine Needle Puncture and Aspiration (FNA) is an examination for the cytopathological study of a lesion, usually a tumor, of the thyroid or another organ. A needle with a thinner gauge than that used for intramuscular injections is used for this purpose, which is also usually somewhat shorter. It is usually aspirated with a syringe attached to the needle, and nowadays, the physician performing the FNA is assisted by ultrasound imaging of the gland. In this way, he can know exactly when the tip of the needle is inside the lesion to be analyzed. Nowadays the FNA of the thyroid is usually performed by a specialist in Endocrinology or a radiologist.

One or more droplets containing thyroid cells are collected in the aspirate. Once this content has been prepared on crystals, the sample is sent to an anatomopathologist. The latter must diagnose the benignity, malignancy or doubtful status of these cells and issue a report, with which the patient returns to the endocrinologist so that the appropriate measures can be taken.

In the following figures, in the first one the physician holds in one hand the ultrasound probe that will allow him to see the gland, in the other hand the syringe with its needle. The next image shows the image that would be seen on the ultrasound screen where, on the upper right edge, the needle is inserted in the center of the nodule. The last image shows the image to be analyzed and diagnosed by the pathologist.

Patients who are candidates for a thyroid FFPP

The main candidates are those patients who have tumor pathology, i.e. a uninodular or multinodular thyroid. However, before FNA, a thyroid ultrasound should be performed, since it offers us a great deal of useful data to guide the diagnosis and even to know whether FNA is necessary or not. A good ultrasound scanner is important for this, but it is even more important that the images are interpreted by a good sonographer.

These are suspicious data of malignancy:

• the nodule is hypoechoic or cystic with a solid hypoechoic component equal to or larger than 1 cm.
• irregular margins
• it has microcalcifications
• it has a higher than wide shape
• it has rim calcification with small extruded soft tissue component
• that the vascularization on Doppler is irregular and preferably central
• there is evidence of extrathyroidal extension (adenopathy).

All nodules with these characteristics should be sent for FNA. On the contrary, nodules of regular contour, with hypoechoic halo, without microcalcifications, with peripheral vascularization and without loco-regional adenopathies, suggest benignity. When all this series of data is considered, the sonographer issues or should issue a diagnosis based on the TIRADS (Thyroid imaging reporting and data system) classification.

The data of this classification are:

• TIRADS 1 – Normal thyroid. No focal lesion
• TIRADS 2 – Benign nodules. 0% malignancy.
• TIRADS 3 – Nodules probably benign (
• TIRADS 4:

1. 4a – Nodules of uncertain identity (5-10% risk of malignancy).
2. 4b – Suspicious nodules (10-50% risk of malignancy)
3. 4c – Highly suspicious nodules (50-85% risk of malignancy)

• TIRADS 5 – Nodules probably malignant (more than 85% risk)
• TIRADS 6 – Malignancy already detected by biopsy or puncture

In general, nodules smaller than 1cm should not undergo FNA unless they have ultrasound data suspicious for malignancy. TIRADS 3, 4 and 5 should be needled.

What data does FNA provide in thyroid pathology?

By assessing the amount of colloid, follicular cells and cellular atypia, the cytologist issues a report that can be the classic but still widely used 4-group report:

1. colloid nodule (benign)
2. Cancerous nodule (being able to establish the type of cancer)
3. Follicular neoplasm (suspected of follicular cancer)
4. Follicular-colloid neoplasm (uncertain diagnosis, with repeat FNA in about 6 months).

Or also a diagnosis based on the most modern classification in 6 groups called Bethesda (Bethesda Reporting System). This classification includes 6 groups:

• Bethesda 1. Non-diagnostic or inadequate puncture: only colloid or acellular or contaminated with blood. The endocrinologist will assess the repetition.
• Bethesda 2 (Benign). Benign follicular nodules (colloid, adenomatoid) or nodules in the setting of thyroiditis. Risk of malignancy
• Bethesda 3 (Doubtful or indeterminate). There are atypia or unclear follicular lesions mixed with suspicion of malignancy and benignity. Risk of malignancy 5-15%. In these patients it is normal to repeat the FNA after about 6 months.
• Bethesda 4 (Possibility of malignancy). Follicular neoplasia. FNA does not distinguish between adenoma and carcinoma. They should be operated because approximately 20% are cancers.
• Bethesda 5 (Suspected malignancy). Papillary, medullary, anaplastic carcinoma, lymphoma or metastases. Risk up to 75%.
• Bethesda 6 (Malignant). Poorly undifferentiated papillary, medullary, squamous cell carcinoma, anaplastic carcinoma, mixed carcinoma, non-Hodking lymphoma or metastasis. Risk close to 100%.

Bethesda 4, 5 and 6 require thyroid surgery. Bethesda 2 and 3 follow-ups by endocrinologist.

By first of all taking into account the clinical manifestations of nodular thyroid pathology, the family history, an analysis based on the clinical data, ultrasound performed by a good sonographer and the cytopathological study by means of FNA, it is nowadays extremely difficult to make a wrong diagnosis of a lesion. And if the diagnosis is accurate, the treatment cannot be misleading. Therefore, the evolution of these patients depends on getting things right.