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What are the side effects of a thyroid needle biopsy?

A thyroid needle biopsy, also called a thyroid fine needle aspiration (FNA), is a procedure used to collect cells from the thyroid gland for examination under a microscope. This minimally invasive test can help diagnose thyroid nodules or tumors and determine if they are benign or malignant. While thyroid biopsies are generally safe, some side effects can occur.

The thyroid is a small, butterfly-shaped gland located at the base of the neck. It produces hormones that regulate metabolism, growth, and development. Thyroid nodules, which are lumps or tumors that develop inside the thyroid, are quite common. Most are noncancerous (benign), but some are cancerous (malignant).

When a nodule is discovered, a thyroid biopsy is often performed to collect cells for examination. A thin, hollow needle is inserted into the nodule to withdraw samples of cells and fluid. The collected specimens are then looked at under a microscope by a pathologist to determine if cancer is present.

Thyroid FNA biopsies are done on an outpatient basis and take only a few minutes to complete. The procedure is considered safe, with few complications. However, some side effects can occur.

Common Side Effects

Most people experience little to no side effects from a thyroid needle biopsy. However, some common side effects include:

  • Bruising: Bruising at the biopsy site is common and normal. It results from the needle puncturing the skin and tissues.
  • Bleeding: A small amount of bleeding or oozing can occur where the needle entered the skin. Applying pressure stops it quickly.
  • Pain: There may be some mild soreness, swelling, or discomfort at the biopsy site that resolves within a day or two.
  • Infection: Infection is rare but can happen if bacteria enter the biopsy site. Signs include increased pain, redness, swelling, and pus.

These side effects are usually temporary and resolve within a few days after the biopsy. Using ice packs and over-the-counter pain medication can help manage discomfort.

Rare Side Effects

In rare cases, more serious complications can occur:

  • Excessive bleeding: Bleeding is considered excessive if a large hematoma develops or the site continues bleeding after applied pressure.
  • Damage to vocal cords/nerves: The needles can sometimes damage the recurrent laryngeal nerve, which controls vocal cord movement.
  • Thyroid hormone changes: Thyroid hormone levels may fluctuate after the biopsy, causing temporary hyperthyroidism or hypothyroidism.
  • Infection spreading: Though very rare, infection could spread deeper into neck tissues, requiring antibiotics.

The estimated risk of serious complications is less than 1-2%. If any concerning symptoms develop after the biopsy, contact your doctor right away.

Factors Affecting Side Effects

Certain factors can increase the likelihood of side effects after a thyroid biopsy:

  • Nodule location – Biopsies of nodules near the back of the thyroid or close to vital neck structures are more likely to cause problems.
  • Nodule size – Larger nodules may be more difficult to biopsy, increasing injury risk.
  • Underlying health conditions – Bleeding risks are higher in people taking blood thinners or with bleeding disorders.
  • Inexperience of doctor – Less experienced physicians conducting the biopsy have higher complication rates.
  • No ultrasound guidance – Using ultrasound to guide needle placement reduces chances of side effects.

Discuss any underlying health issues and concerns with your doctor before the biopsy. More precautions may be needed to minimize risks.

Recovering from Side Effects

If you do experience common side effects like bruising, pain, or bleeding after a thyroid biopsy, these self-care tips can help:

  • Apply ice packs to reduce swelling and discomfort at the biopsy site.
  • Use over-the-counter pain relievers like acetaminophen (Tylenol) or ibuprofen (Advil).
  • Rest your voice if you experience hoarseness or voice changes.
  • Drink lots of fluids and avoid strenuous activity for a few days.
  • Keep the biopsy bandage in place for the recommended time.
  • Watch for signs of infection like warmth, redness, pus, or worsening pain.
  • Avoid blood thinners, fish oil, vitamin E, and aspirin until bleeding stops.

Symptoms should improve within a few days. Call your doctor if side effects do not go away or get worse. Serious complications like uncontrolled bleeding or spreading infection require urgent medical care.

Results and Next Steps

It takes about 1-2 weeks to get the results of the thyroid biopsy back from the lab. Your doctor will go over the pathology report with you and explain what it means.

Possible results include:

  • Benign (noncancerous): No concerning cells are seen. You can continue thyroid monitoring.
  • Malignant (cancerous): Cancerous cells are found. Treatment like surgery will be recommended.
  • Indeterminate: The results are unclear if cells are cancerous or not. A repeat biopsy or molecular testing of the sample may be done.
  • Non-diagnostic: The specimen did not contain enough cells to make a diagnosis. Another biopsy is needed.

If thyroid cancer is diagnosed, your doctor will discuss treatment options like surgery, radioactive iodine therapy, hormone treatment, radiation, or chemotherapy.

The thyroid biopsy provides important information to determine if a nodule is benign or malignant. Being aware of potential side effects can help ensure proper recovery and follow up care.


Thyroid needle biopsies are generally safe, fast, and well-tolerated. Bruising, pain, and bleeding at the biopsy site are common but temporary side effects. Rare risks like nerve damage or hematoma formation occur in less than 1-2% of biopsies. Recovery typically takes only a few days. Contact your doctor if any worrying symptoms develop or persist. Proper aftercare helps minimize complications so you can get an accurate diagnosis and receive appropriate treatment if thyroid cancer is found.

Tables Comparing Thyroid Biopsy Side Effects

Here are some tables comparing the common, rare, and risk factors for side effects of a thyroid needle biopsy:

Common Side Effects Rare Side Effects
  • Bruising
  • Bleeding
  • Pain
  • Infection
  • Excessive bleeding
  • Nerve damage
  • Thyroid hormone changes
  • Spreading infection
Lower Risk Higher Risk
  • Nodules in front of thyroid
  • Small nodule size
  • No health conditions
  • Experienced physician
  • Ultrasound guidance
  • Nodules near back/neck structures
  • Large nodule size
  • Clotting disorders
  • Inexperienced physician
  • No ultrasound

These tables illustrate that while minor side effects are common, serious risks are infrequent. Proper precautions can help reduce the likelihood of complications.