Is your Multinodular Goiter Actually a Substernal Goiter? 

What is a Multinodular Goiter?

You may ask yourself, what is a multinodular goiter? Are thyroid nodules the same thing as a multinodular goiter? What is this lump in my neck? Why are doctors telling me that I have a substernal goiter, but I don’t see anything in my neck? These are all appropriate questions and can be answered in this blog. A goiter just means “big thyroid” and a multinodular goiter means that the thyroid has many nodules giving you an enlarged thyroid. A multinodular goiter is a thyroid that has grown to a large size.  The nodules themselves are not the goiter, but in fact the whole thyroid containing the nodules is the enlarged thyroid or multinodular goiter. When the goiter is in the neck, then you will likely notice it as a lump in your neck.  Other goiters can grow into your chest and are called substernal goiters. Substernal means “below the sternum” or below the collar bone and therefore into the chest.  A substernal goiter is therefore a large thyroid that has grown so big that it has grown out of the neck and into the area of the chest.

What is a Substernal Goiter?

A substernal goiter is when the thyroid has abnormally enlarged over time and has grown below the collar bone and into your chest.  This is not something that occurs over the course of several weeks or months.  It usually occurs over the course of years.  The most common cause of substernal goiters are long standing multinodular goiters that have grown over many, many years into the chest cavity. The incidence of substernal goiters among patients with multinodular goiters is reported to range from approximately 5-15%.

The most common symptom or complaint of a multinodular goiter is the cosmetic appearance of a large lump in the neck or the symptoms produced by the actual size of the goiter. However, substernal goiters may not produce a lump in the neck because they may not grow outward.  The substernal goiter may actually grow inwards toward the back portion of your neck and down into the chest area. Symptoms related to the size of the goiter may include a sense of a lump in the throat, difficulty swallowing, difficulty breathing and even in extreme cases, voice changes and even a completely hoarse voice.

Symptoms of Substernal Goiters

Symptoms of substernal goiters are very easy to identify if you are aware of where the thyroid actually is in your body.  The thyroid sits on top of the trachea (windpipe) and esophagus (swallowing tube), and then grows below the collar bone into your chest.  When the multinodular goiter grows to a large size, it compresses these structures in the neck.  Therefore, the symptoms are called compressive symptoms including difficulty breathing, swallowing, needing to clear your throat, and an overall tightness in your neck (especially while laying down).  Other more severe symptoms are stridor or wheezing.  These are likely due to the fact that the multinodular goiter is so big on both sides of the windpipe that it is compressing the windpipe. The thyroid also sits on top of the nerves that go to the voicebox.  Compression of these nerves can cause hoarseness. There is also a specific sign called a Pemberton sign. This sign is a combination of specific symptoms all happening at the same time.  Pemberton’s sign is a positional sign described by Dr. Pemberton in the 1940’s.  It occurs when you raise your arms above your head, turn your head to the right or left, or when you are laying down.  These positional changes cause facial flushing (redness of the face), trouble breathing, and possible stridor.  This occurs as a result of the thyroid goiter being drawn into the bony chest cavity.

Are Symptoms of Substernal Goiters Different Than Regular Goiters?

These symptoms of a substernal goiter do not differ greatly from those of patients with a multinodular goiter that are only in the neck, but they may be more severe because of the presence of the mass within the bony chest cavity.  The bones in the chest are immobile and if a goiter is growing below the sternum, then it has to compress the softer structures because it cannot compress the sternum and the ribs.

However, some patients with a substernal goiter do not have symptoms.  These patients come to find out about their substernal goiter incidentally by a scan performed for different reasons.  For example, patients can be getting a CAT scan of their chest for chest pain or for pneumonia and a substernal thyroid mass appears on the scan.  This should then prompt a proper evaluation of your thyroid with an expert surgeon.

What Are The Next Steps if I Am Told I Have A Substernal Goiter?

Evaluation of a substernal goiter, as with any medical evaluation, starts with a proper history and physical.  Important things to note in your family history is if someone in your family has had a diagnosis of a multinodular goiter, thyroid cancer, or other endocrine cancers.  Of course, any other serious medical conditions unrelated to your goiter should also be discussed at this time. The physical exam would occur next where your physician actually feels your neck. Feeling your neck gives more information about the mutinodular goiter including the size and firmness of your thyroid and any enlarged lymph nodes in your neck.

Another portion of the physical exam for your goiter is something called a laryngoscopy.  This is an examination of your voicebox with a small lighted microscope. It is used to look at the voice box to determine how the vocal cords of the voice box are functioning. Even though a patient does not report change in their voice does not ensure that the vocal cords are working normally. A vocal cord that is paralyzed greatly increases the concern that a multinodular or substernal goiter may be hiding a thyroid cancer.

• Blood tests for thyroid function and specific thyroid antibodies is also part of the evaluation.  We obtain TSH, T4, thyroglobulin, and thyroglobulin antibodies on a routine basis.  T3 and Thyroid stimulating antibody will be added on for specific cases. You should make sure you are being evaluated by a thyroid expert.
  
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The next step would be imaging with a high resolution ultrasound.

Substernal Goiters Should be Evaluated with a High Resolution Ultrasound

Substernal goiters, like all goiters, should have a thorough neck ultrasound exam to look at the entire goiter and the lymph nodes on both sides of the neck.  If a worrisome nodule is found within the goiter, a needle biopsy may need to be performed. Needle biopsy is only indicated if there is a mass within the multinodular goiter which is suspicious for malignancy. During a needle biopsy, the ultrasound helps make sure they are getting cells from the right areas. Sometimes a multinodular goiter or even a substernal goiter can only take up half the thyroid gland—with the other half of the thyroid being normal in size and not extending into the chest.  If the whole thyroid is not being surgically removed, needle biopsy is generally done on all thyroid nodules that are big enough to be felt. This typically means that they are larger than about 1 centimeter (about 1/2 inch) across. Needle biopsies of swollen or abnormal appearing lymph nodes in the neck may be more informative than the thyroid nodule itself in obtaining a diagnosis. After the biopsy is performed, a special pathologist is used to look at the cells under a microscope to tell if they are cancerous or benign. 

Substernal Goiter: When is a Radioiodine Scan Ordered?

One of the reasons to obtain blood tests during your evaluation of your multinodular goiter is to test the thyroid function.  If your thyroid function is high, meaning a high T3 and T4 (and a suppressed TSH), your thyroid is hyperfunctioning. You, therefore have a diagnosis of hyperthyroidism. This would be the only reason to order a radioactive iodine scan (thyroid scan) if you have a substernal goiter. In these cases, the thyroid stimulating hormone (TSH) will be very low and in cases of Graves’ disease, the thyroid stimulating immunoglobulin will be very high. The thyroid goiter patient may or may not have recognized symptoms of their hyperthyroidism.

• The thyroid scan can also differentiate between hot nodules (toxic nodules), a toxic multinodular goiter, and Graves’ disease. This differentiation helps us determine which type of surgery is best for you. A toxic nodule will only require a lobectomy unless you have nodules on the other side that are suspicious for thyroid cancer.  Toxic nodules or hot nodules themselves are almost always non-cancerous but the preferred management of hot nodules is frequently surgery since it is a clear, safe and 100% effective therapy for the hyperthyroidism.  If the scan shows multiple hot nodules throughout the thyroid, then you have a toxic multinodular goiter and your whole thyroid will need to be removed.  Graves’ disease shows a diffuse increased uptake throughout the thyroid gland and will also require total removal of your thyroid gland.

CT Scan is the Next step for a Substernal Goiter

With a substernal goiter, neither the physical examination nor ultrasound can completely determine how far the goiter actually goes. Physical exam and ultrasound cannot feel or see below the collar bone. Therefore, a CT scan should be ordered and will be the next step after an ultrasound. The CT scan will show areas that the substernal thyroid goiter extends and prepare the expert thyroid surgeon for their safe and effective approach to remove all of the substernal goiter and spare all other important structures.

Substernal Goiters Need Surgery

Substernal thyroid goiters clearly need surgical management. There are many indications for removal. The first indication is the shear size of the multinodular goiter causing a visible mass in the neck.  A second major reason is that the goiter may be producing symptoms of difficulty breathing or swallowing. In some scenarios, the substernal goiter could be producing excessive hormone and be “toxic” to your body.  Multinodular nodules can also harbor a thyroid cancer and need removal to cure the malignancy.  Lastly, multinodular goiters that are growing or have failed medical management (RAI treatment) need surgical intervention.

Even though a substernal goiter may extend extensively below the sternum (collar bone) and go well into the chest, these goiters can almost routinely be removed through a relatively straight forward incision, in the lower neck, right above your collar bone. If your surgeon is telling you that they need to "split your chest" or "open your sternum", make sure that you have identified a highly experienced thyroid surgeon. Again, such approaches are almost never actually required.

The above photos show a CT scan of the neck and a substernal thyroid goiter after it has been removed from the neck and chest.  This thyroid goiter essentially fills the entire neck and extends into the upper chest surrounded by the blood vessels leaving the heart and veins leading the return of blood to the heart.  This requires a straight forward surgery by an expert thyroid surgeon with a lower neck collar incision and leaving the hospital the very next morning.

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