Most thyroid cysts are completely benign and nothing to worry or stress over.
But some cysts may contain cancerous cells which require more aggressive treatment.
This guide will teach you everything you need to know about thyroid cysts including symptoms, management, and how to determine if your cyst is cancerous or not.
What is a Thyroid Cyst?
It’s helpful to think of a thyroid cyst as a subtype of a thyroid nodule.
A thyroid nodule is simply a growth on your thyroid gland which is found in your neck.
Thyroid cysts are a type of thyroid nodule which is entirely filled with “fluid”.
These cysts can range in size from very small to very large.
They also vary in how they look on ultrasound.
Cysts which are large and entirely filled with fluid are almost always benign (nothing to worry about).
Some cysts, referred to as complex cysts, contain a combination of solids and fluid inside the nodule itself and these have a higher risk of being cancerous (1).
You will most likely not know you have a thyroid cyst unless you have a thyroid ultrasound.
The reason for this is that thyroid cysts feel just like solid thyroid nodules during the examination and it’s only during thyroid ultrasound that they can be differentiated.
The biggest concern that most people have when it comes to thyroid cysts is whether or not they are cancerous or dangerous.
Most of the time they are nothing to worry about but we will discuss some of the treatment options below.
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Do Cysts Cause Symptoms?
In fact, they are almost always picked up by routine exams and most patients are surprised to know that they have a nodule or cyst on their thyroid.
Some thyroid cysts may cause symptoms if they are too large or if they grow too quickly.
These types of cysts may cause issues with swallowing or pain in the neck because of their size.
If your cyst is cancerous it may also cause issues such as enlargement of the lymph nodes in your neck area (but remember this is not common).
Below you can find a list of symptoms that may be associated with thyroid cysts:
- Most cysts and nodules are asymptomatic (meaning they are not associated with any symptoms).
- Some cysts may be large enough to cause pain when swallowing or a sensation that something is in your throat.
- If a cyst is cancerous it may also cause an enlargement of lymph nodes in your neck area which can be firm.
- Other large cysts may cause pain, changes to your voice (usually hoarseness), difficulty when breathing and pain in the thyroid gland (but these are less common).
For the most part, you will probably not have any symptoms if you have a thyroid cyst.
How Are They Treated?
Treating thyroid cysts largely depends on a few very important factors:
Is the thyroid cyst “simple” (3) on ultrasound imaging? (small cysts less than 3cm in size can usually be monitored)
Is the thyroid cyst “complex” (4) on ultrasound imaging? (Complex cysts usually require a biopsy or needle aspiration to rule out cancer)
Is the thyroid cyst small or large? (5) (Small cysts usually do not cause any symptoms but large cysts may require treatment to help alleviate symptoms)
Does the cyst appear solid or completely fluid-filled? (The more solid your cyst is the more likely it is to have cancerous cells and thus may require a biopsy or aspiration)
The answers to these questions will help determine how aggressive you should be in treating your cyst.
The more benign your cyst looks the more conservative you can be.
If your cyst is large, causing symptoms or suspicious for cancer then you may need to be more aggressive.
You can find a list of treatments below from most conservative to least conservative:
#1. Careful Monitoring
If your cyst is simple, small, and does not have any features that may increase the risk of thyroid cancer then your doctor may simply recommend the “wait and see” approach.
This approach is very common because up to 15% of simple thyroid cysts may completely resolve on their own and most cysts do not grow or become larger over time.
Other small and simple cysts just need to be monitored and checked out with semi-frequent ultrasound tests (every 6-12 months) to ensure that they are not getting bigger.
In many cases, it may cause more harm than good to stick a needle into your thyroid or to try and remove it via surgery as opposed to simply monitoring it over time.
#2. Fine Needle Aspiration
Sometimes, large cysts may need to be drained with a procedure known as fine needle aspiration.
This is a small procedure in which a needle is placed through the skin (guided by ultrasound) into your cyst where a syringed is used to “suck out” the fluid inside.
This procedure is usually very quick and not as painful as it sounds.
Typically fine needle aspiration is used if your cyst is either very large or if your Doctor wants to ensure that the cyst does not contain cancerous cells.
The main reason that this procedure is not used on all cysts is that even after the fluid inside a cyst is removed, up to 85% of the time the fluid will come back rendering the procedure ineffective.
But, if you need to know if your cyst is cancerous (or if the cyst is very large) then this procedure may be necessary.
If aspiration of the cyst does not work then your doctor may recommend an ablative procedure with something like ethanol.
During this procedure, a small amount of a caustic agent is inserted into your cyst with the hopes that it destroys the fluid-producing cells.
#4. Thyroid Surgery
As a last resort, your doctor may recommend thyroid surgery or complete removal of the cyst (7).
This is not typically used to treat thyroid cysts unless they are very large, causing severe symptoms or if other less invasive procedures have failed.
Thyroid Cysts & Thyroid Function
One of the concerns that many people have is that of thyroid function.
Your thyroid controls many very important functions in your body ranging from your body temperature to your metabolism and even your heart rate.
These functions are regulated by thyroid hormone which is produced by the thyroid gland.
Because of this, it’s natural to think that problems with the thyroid gland itself may cause problems in the production of thyroid hormone.
Luckily, when it comes to thyroid nodules and thyroid cysts this is rarely the case.
Most thyroid cysts do NOT cause any problem with your thyroid gland or its ability to function and create thyroid hormone (8).
In some rare cases, if your cyst/nodule is large enough or if it is cancerous it may cause local damage to thyroid gland tissue but this is very uncommon.
If you have a thyroid cyst and you are experiencing symptoms such as fatigue, weight gain, cold skin, constipation or other symptoms of hypothyroidism, then you can easily check your thyroid function with some simple and routine thyroid blood tests.
These tests will help determine if your thyroid is functioning normally.
Can Thyroid Cysts be Cancerous?
The main concern, from your perspective and from your Doctors, is whether or not your thyroid cyst is cancerous.
This is the most important question that both of you should have.
Because if there is any suspicion that your cyst is cancerous then it completely changes how you look at the nodule and how you should approach treatment.
The main goal when determining how to treat or what therapies you should use comes down to how likely you think that your cyst is cancerous.
But are most cysts cancerous?
It turns out, that much like thyroid nodules, most thyroid cysts are NOT cancerous.
But because you never want to miss the diagnosis of cancer, your Doctor will probably at least order an ultrasound to evaluate your cyst just to make sure.
Because cancers alter how your cells normally function, it is possible that cancer cells may be more likely to produce fluid when compared to normal thyroid cells.
These changes to your cells, if cancer is present, can sometimes be identified early based on how they look under ultrasound imaging.
Features such as how large your cyst is, if it is completely fluid-filled or partially fluid-filled, if it has blood flow in it, and so on may help predict how likely your cyst is to be cancerous (9).
The more abnormal results that are seen on ultrasound the more likely your cyst may be cancerous and the more aggressive your Doctor will be with treatment.
Up to 5% of all fine needle aspirations contain cancerous cells (10) but this percentage varies based on your age (the older you are the more likely your cyst is to be cancerous).
Your Next Steps
What should you do if you suspect you have a thyroid nodule or a thyroid cyst?
You can follow the steps below to ensure that you are getting the proper care:
- Go get a complete history and physical exam from your Doctor. This may include feeling your thyroid gland to ensure it is not abnormal.
- If necessary you may need an ultrasound to help identify any abnormal features of your cyst. An ultrasound will help you know the size of your cyst and if it is considered a simple cyst or a complex cyst.
- Check your thyroid function if you are experiencing symptoms such as fatigue, weight gain, or depression. Tests such as the TSH, free T3, and free T4 can help determine if your thyroid is functioning normally.
- If necessary obtain a fine needle aspiration of your cyst to determine if there are any cancerous cells inside.
- Determine how to proceed with treatment. Do you need to watch or monitor your cyst with frequent ultrasounds or do you need to try and remove the fluid inside?
- Periodically check on your thyroid gland with doctors’ visits and feeling of your neck/thyroid gland over time.
Thyroid cysts are not as common as solid thyroid nodules but they are still important to understand.
It’s helpful to think of thyroid cysts as a subtype of thyroid nodules but one that is usually completely filled with fluid.
The majority of cysts are benign and not dangerous.
Some cysts, if they have abnormal features, may be cancerous and may require more aggressive treatment.
Treatment ranges from watchful waiting and monitoring to complete removal.
If there is any doubt if your cyst contains cancer then your Doctor will check for cancerous cells with a fine needle aspiration.
Now I want to hear from you:
Do you have a thyroid cyst?
Are you experiencing any symptoms?
What treatment have you undergone?
Leave your comments below!