Fine needle aspiration

What is Fine-Needle Aspiration (FNA), also known as Fine-Needle Aspiration Biopsy (FNAB)?

• It is the extraction, through aspiration, of a partial tissue sample to be examined under a microscope by a cytopathologist or a pathologist trained in this technique, for the detection of cancer.
• It is a minimally invasive procedure, used for many years to obtain enough cells to make a microscopic diagnosis of tumors located in easily accessible areas, such as the breast, thyroid, oral cavity, salivary glands, lymph nodes, soft tissues, etc.
• Aspirations can also be performed on non-palpable masses, guided by ultrasound, or even on some thoracic or abdominal tumors, guided by CT scans, in a team effort consisting of a pulmonologist or surgeon, cytopathologist, and radiologist.
• Some cystic lesions (which are hollow with fluid inside) can be aspirated for decompression when they are large and bothersome to the patient.

What is the difference compared to conventional surgical biopsies?

Unlike habitual biopsies taken with a scalpel or thick needles, where solid tissue is obtained and processed with techniques that take several days, with the fine-needle technique the material obtained consists of only a few drops of isolated cells detached from the tissues during aspiration. Therefore, its examination is faster, less painful, and less invasive.

When to perform Fine-Needle Aspiration and not an open or invasive surgical biopsy?

FNA is primarily indicated for palpable tumors or masses, easily accessible with a thin needle. They are the first step to obtain a preliminary diagnosis in palpable tumors or cysts, with very little risk, and can be done in an examination room or ultrasound suite. This allows the treating physician to thoroughly plan the subsequent treatment, depending on a benign or malignant result, without "seeding" the tumor in adjacent tissues, as the needles are very thin.

In a few instances, it may not be possible to obtain tissue via FNA, in which case it can be attempted again later or through another type of procedure.

Should FNA always be guided by ultrasound?

• Some masses, such as those in the thyroid, whether palpable or not, should always be guided by ultrasound to understand the tumor's characteristics and avoid passing through hollow, fluid-filled areas (cysts), which usually do not contain material of diagnostic interest, and to take the sample from solid areas where the material should be obtained. Ultrasound directs the needle precisely to the exact point where the most important part of the tumor is suspected to be. Several samples are usually taken.
• The minimum size of a thyroid tumor to perform an FNA is 1.0 cm.
• In other organs such as the breast, soft tissues, oral cavity, and lymph nodes, if the lesion is sufficiently palpable to be held and punctured, ultrasound guidance may not be strictly necessary. However, it is preferable that the patient already has an ultrasound study prior to sampling.
• In the case of a breast puncture, it is desirable for the patient to have a recent mammogram, if their age permits.

Who performs the FNA procedure?

• Preferably a cytopathologist, who is a pathologist with sub-specialty training in the study of isolated cells. In addition to performing the aspiration with the appropriate technique, they can verify the aspirate under the microscope at that precise moment to ensure the sample is sufficient in quality and quantity, thus avoiding a repeat procedure.
• It may also be performed by a physician of another specialty who has training and experience in this technique, preferably advised on-site by a pathologist to verify the quantity and quality of the sample and prevent inadequate material for diagnosis.

What are the advantages of FNA?

• It is an accessible, low-cost examination.
• Does not require hospitalization.
• It is very tolerable and minimally painful, as a local cutaneous anesthetic is applied.
• It is fast, and results can be available in 24-48 hours.
• Helps plan the optimal treatment approach by separating lesions into benign and malignant, allowing the treating physician to remove the tumor with wider margins if the result is cancer, or subject it to another type of procedure if it is suspicious of cancer.
• Faster management in cases of infectious types, such as some fungi or tuberculosis, in the case of masses in lymph nodes.
• It has a sensitivity of up to 95% for cancer detection.

What discomfort or complications might the patient experience after FNA?

- Minimal discomfort such as slight pain or numbness at the puncture site, tingling, and occasionally a small bruise.

- Less frequently, there may be minimal bleeding that easily stops with slight pressure, application of ice, and placing a small bandage.

- Allergic reactions to the cutaneous anesthesia (cream or intradermal injection).

Does it require special care?

• Prior to thyroid FNA, it is recommended not to ingest anticoagulants for a short time beforehand.
• Fasting is not required, but preferably at least a couple of hours after having ingested food, in the case of a thyroid puncture.
• After an FNA, only relative rest is recommended for the remainder of the day of the puncture, the application of ice once, and an analgesic in case of pain.