What Does a Bethesda 3 Thyroid Biopsy Result Mean?

A Bethesda 3 thyroid biopsy result means the cells taken from the nodule showed some changes that the pathologist could not confidently call either benign or suspicious. The category is called atypia of undetermined significance (AUS). Most nodules with this result turn out not to be cancer, and the usual next step is more information, often a repeat fine-needle aspiration (FNA) or molecular testing, rather than immediate treatment.

The Bethesda system is the standard way pathologists report thyroid FNA results. It has six categories, from nondiagnostic (not enough cells) through benign, AUS, follicular neoplasm and suspicious, to malignant. Older reports may use the longer label AUS/FLUS, where FLUS stands for follicular lesion of undetermined significance.

This guide is for adults who already have a Bethesda 3 report. It explains the terms and options so you can talk them through with your care team; it cannot interpret your own sample.

A Bethesda 3 result on its own is not an emergency. Some symptoms still need prompt attention whatever the biopsy showed. The NHS advises seeking urgent medical help if you are having difficulty breathing or are more short of breath than usual. If breathing becomes very difficult, call your local emergency number.

Contact your clinician sooner rather than waiting for a routine follow-up if you notice any of the following.

• A neck lump that is getting bigger, or new pain or a feeling of pressure in the front of the neck.
• A hoarse voice that is not getting better.
• Difficulty swallowing that is not getting better.
• After the biopsy: fever, chills, or redness, swelling or pus at the needle site, which Cleveland Clinic lists as possible signs of infection.

Usually not. Cleveland Clinic states that about 5% to 15% of nodules with an AUS result are cancerous. The 2015 American Thyroid Association (ATA) guideline gives the same predicted range for this category.

These are group estimates, not an individual prediction. The ATA guideline notes that some studies found a higher rate in this category than predicted, and figures vary between laboratories and between editions of the reporting system. Ask your team how they interpret the result alongside your ultrasound findings, because the scan pattern changes the picture.

For comparison, Cleveland Clinic describes benign as the most common biopsy result, at about 70% of all thyroid biopsies.

The National Cancer Institute also notes that thyroid nodules are common but usually are not cancer. A Bethesda 3 result is a reason to gather more information, not a diagnosis.

The ATA guideline says a repeat FNA gives a more definitive answer in many cases. A second sample may come back clearly benign, stay in the same category or, less often, move to a more concerning category. The guideline also notes that pathologists vary quite a lot in how they use this category, so a review of the slides by an experienced thyroid pathologist can sometimes reclassify the result.

The US National Cancer Institute (NCI) suggests patients can ask for biopsy samples to be checked by a pathologist with experience in diagnosing thyroid cancer. Asking about this is reasonable, not a sign of distrust.

A repeat biopsy is done the same way as the first, usually with ultrasound guidance. Ask how long you should wait before it and when results usually arrive; Cleveland Clinic says most people get results within about a week.

Molecular testing looks for gene changes or gene activity patterns in cells from the nodule. It is often done on extra material collected during an FNA. The ATA guideline says that, after considering worrying clinical and ultrasound features, repeat FNA or molecular testing may be used to add to the risk assessment instead of going straight to surveillance or surgery. It also says informed patient preference and feasibility should be part of the decision.

Different tests work in different ways. According to the ATA guideline, some are better at suggesting a nodule is likely benign, while others are better at pointing towards cancer, and no single test reliably rules cancer in or out. Availability and cost also differ by country and health service.

Ask which test is offered, what a negative or positive result would change in your plan, and whether insurance or your health service covers it.

If repeat FNA or molecular testing is not done or does not give a clear answer, the ATA guideline says either surveillance or diagnostic surgery may be chosen, depending on clinical risk factors, the ultrasound pattern and patient preference.

Surveillance usually means repeat ultrasound scans to check for growth or change. When surgery is considered for a single indeterminate nodule, the ATA guideline recommends removing one lobe (a lobectomy) as the usual first operation. The removed tissue is then examined in full, which gives a definite diagnosis that a needle sample cannot.

If you are offered surgery, the separate guide on Bethesda 4 nodules explains lobectomy in more detail, including the risks the ATA lists.

Take the full cytology report and the ultrasound report to your appointment. These questions can help you leave with a clear plan.

• What exactly does my cytology report say, and is it the AUS category under the current reporting system?
• What did the ultrasound show, such as the TI-RADS score and nodule size, and how does that affect the plan?
• Do you recommend a repeat FNA, molecular testing, ultrasound follow-up or surgery, and why?
• Could an experienced thyroid pathologist review the slides?
• If I choose surveillance, when is the next scan and what change would prompt action?
• Who will contact me with results, and by when?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with an AUS result moved through repeat biopsies, molecular tests or scans can help you notice questions you had not thought of, such as how long people waited between tests.

Other people's cases cannot tell you what your nodule is, and their outcomes do not predict yours. Use what you read to prepare questions for your own care team, who know your scan and history.