Is It Necessary To Get A Biopsy For Thyroid Nodules?
Published May 5 2014
From time to time I’ll receive a question from someone who has one or more thyroid nodules about whether or not they should get a biopsy. Of course their main concern is that the thyroid nodule will be cancerous. Just like any other procedure, everything comes down to risks vs. benefits. And while there is a small risk with obtaining a biopsy, it still is an invasive procedure, and it doesn’t always rule out a malignancy. On the other hand, there is also a risk of not getting a biopsy and then finding out at a later time that you have a cancerous nodule. In this article I will give my opinion about whether a biopsy is necessary.
Before I talk about whether getting a biopsy is necessary, let’s first talk about thyroid cancer. There are a few different types of thyroid cancer, including papillary thyroid cancer, follicular thyroid cancer, medullary thyroid cancer, and anaplastic thyroid cancer. I’m not going to discuss the different types, but if you want more information I would recommend taking a look at the article “Thyroid Cancer Types, Stages and Treatment Overview“. Of the four different types of cancer I listed, papillary cancer is the most common type of cancer, with follicular cancer being the second most common. The chances of long-term survival is high with the first three types of cancers, whereas anaplastic is more aggressive.
Fine Needle Aspiration vs. Core Needle Biopsy
Fine-needle aspiration biopsy (FNA) is the standard test used to determine whether surgical removal of a detected nodule is recommended (1). This procedure uses a long and thin needle to obtain a sample of the thyroid tissue. Some people who never have received a biopsy are concerned about whether or not there will be any pain during the procedure. Since I’ve never had this type of biopsy I can’t tell you from self experience what it feels like, although some people claim that the local anesthetic used resulted in very little pain, while others claim that there is a burning type of pain associated with the injection.
Five potential, although rare complications of thyroid fine needle biopsies include 1) cyst fluid leakage; 2) anaphylactic reaction; 3) pneumothorax; 4) thromboembolism and 5) needle tract seeding of medullary thyroid carcinoma (MTC) or thyroid lymphoma (2)
Although the fine-needle aspiration biopsy is the most commonly used diagnostic method for evaluating thyroid nodules, a core needle biopsy might be more beneficial for the diagnosis of papillary thyroid carcinoma and other non-follicular thyroid lesions (3). A few different trials have confirmed that a core-needle biopsy is more useful after a patient has received an FNA of a thyroid nodule which revealed inconclusive diagnostic results (4) (5) (6).
When Should Someone Receive A Thyroid Biopsy?
Many people have thyroid nodules. The good news is that most of these are benign. Although the incidence of thyroid cancer does seem to be increasing, overall it is still rare. Over the years I’ve worked with hundreds of patients with thyroid and autoimmune thyroid conditions, and a few of them were diagnosed with thyroid cancer. So while the risk is low, this doesn’t mean it’s not a concern. For example, I once had a patient who had a thyroid nodule and was following a natural treatment protocol for a number of months. She was receiving some good results, but the thyroid nodule didn’t decrease in size, and so after getting it biopsied they found out that she had thyroid cancer, and she ended up receiving a thyroidectomy. Although it was disappointing that she had to have her thyroid gland removed, it was of course great news that the cancer didn’t spread.
This story isn’t meant to scare people who have one or more thyroid nodules into getting a biopsy. The truth is that there are risks of not getting a biopsy, but as I mentioned earlier, a biopsy is invasive, and doesn’t always rule out a malignancy. Plus, while the incidence of papillary thyroid cancer is increasing, this might be due to widespread overdiagnosis (7), and for obvious reasons might be more commonly diagnosed in those who have healthcare benefits.
For those who are considering having a biopsy done, I would read the article “Too Many Unnecessary Thyroid Biopsies Performed“. This is based on a report in JAMA internal Medicine (8) which involved 8806 patients, and three ultrasound nodule characteristics—microcalcifications, size greater than 2 cm, and an entirely solid composition—were the only findings associated with the risk of thyroid cancer. Based on these findings the authors of the study suggested that rather than performing a biopsy of all thyroid nodules larger than 5mm, one should instead require two abnormal nodule characteristics to determine if someone should require a biopsy. They mention how this would reduce unnecessary biopsies by 90% while maintaining a low risk of cancer.
To summarize, according to the study above, if someone has a thyroid nodule and is concerned about it being malignant, it probably would be best to hold off on getting a biopsy unless if they had at least two of the following three characteristics:
1) Microcalcifications of the thyroid nodule
2) A nodule size greater than 2 cm
3) An entirely solid composition
I also would probably recommend getting the thyroid nodule evaluated if the person has a family history of thyroid cancer. So if someone has a thyroid nodule, and if the nodule only has one of the three characteristics I mentioned, or perhaps even none of these characteristics, they still might want to consider getting a biopsy if they have a family history of thyroid cancer. Of course they can always try finding out if the family member who was diagnosed with thyroid cancer had any of these nodule characteristics, but assuming they are unable to find out this information it might be best to get the nodule biopsied.
Is Genetic Testing For Thyroid Cancer An Option?
One of the major drawbacks of FNA is that in up to 30% of cases the results don’t clearly show whether the nodule is benign or malignant. It’s bad enough to go through such an invasive procedure, but then to find out that it’s inconclusive is very frustrating, to say the least. If the FNA is inconclusive then the person can then get the core-needle biopsy as a follow-up, but this of course involves yet another injection. There are a few other options to help rule out a malignant thyroid nodule.
One example is the Afirma Thyroid FNA Analysis. This involves something called a Gene Expression Classifier (GEC), which measures the expression of 142 genes and applies a multi-dimensional algorithm to reclassify a nodule which produced indeterminate results as benign or suspicious (9). A study published in the New England Journal of Medicine demonstrated that thyroid nodules with indeterminate cytopathology and benign GEC results have less than 6% likelihood of being malignant (9). And so genetic testing still isn’t 100% accurate when it comes to ruling out thyroid nodule malignancies, but it can be more accurate than just doing an FNA biopsy. Another example is the miRInform Thyroid panel, which analyzes a panel of 7 molecular markers most commonly encountered in thyroid cancers (10).
In summary, when someone has a thyroid nodule, it can be difficult to determine whether it is necessary to obtain a biopsy. I think most of the time getting a biopsy is unnecessary. Thyroid cancer is rare, and out of the four different types of thyroid cancer, only one of them is commonly aggressive. Plus, getting a thyroid biopsy doesn’t always confirm the presence of a benign or malignant nodule, as the results frequently are inconclusive. Research shows that most malignant thyroid nodules show at least two of three characteristics (microcalcification, nodule size greater than 2 cm, an entirely solid composition), and so this should help people determine whether or not getting a biopsy is necessary. In some cases, genetic testing might also be considered as an option to rule out thyroid cancer.