Thyroid nodules are growths that occur in the thyroid gland forming a lump or bump within the otherwise smooth, even thyroid. Thyroid nodules are common, occurring in 40% of women and 30% of men during their lifetime. Overall prevalence of thyroid nodules in the general population has been estimated as high as 65-68% based on autopsy studies. Most thyroid nodules are benign, but some are cancerous (roughly 5%). Benign nodules as well as cancerous nodules grow. As these nodules enlarge, some need to be removed with surgery just based on size alone. 

Learn more about the top things patients worry about with thyroid nodules.

Top 4 Things to Know About Thyroid Nodule Size

Patients worry about thyroid nodule size as these tumors get bigger, cause symptoms, or become noticeable. Clearly, thyroid nodule size matters. Thyroid nodule size, however, does not always tell the whole story. Below I will discuss the top 4 things to know about thyroid nodule size.

#1 Thing to Know About Thyroid Nodule Size: Thyroid Nodule Size Matters and Predicts Need for Surgery

As thyroid nodule size increases, the need for surgery does as well.  When not considering other parameters such thyroid cancer, thyroid function, etc., the size of a nodule can reliably predict the need for surgery as seen in Figure 1. This figure clearly shows an increasing likelihood for surgery as thyroid nodule size increases (independent of other factors). Importantly, thyroid nodule size, however, does not directly correlate with the nodules being malignant. While the risk for cancer and spread to lymph nodes increased with large nodules (10.4%- 22%), not all big nodules are cancerous. Certainly, patients worry more about thyroid nodule size as these tumors grow, but not all, or even the majority of large nodules are cancerous, but the majority of large nodules will eventually require surgery.

Figure 1: Thyroid nodule size chart shows that the likelihood for requiring thyroid surgery increases as the size of the thyroid nodule increases. When the thyroid nodule reaches 4 cm or greater, it will almost certainly require surgical treatment.

As thyroid nodule size increases, these masses crowd out/replace normal thyroid tissue. As seen in Figure 2, which shows common food items size relative to thyroid nodules, once these nodules reach the approximate size of a lemon, they are as big or bigger than a normal half of a thyroid gland. These nodules require surgery (see # 2 below).  Very large nodules rarely need to be biopsied because surgery is indicated to remove these lesions based on thyroid nodule size alone. Nodules the size of a grape or small kiwi usually require a needle biopsy for further information. Nodules the size of a peanut or pea can also require a biopsy if there are suspicious features noted on ultrasound (more on that in # 4 below). Sometimes, smaller nodules require thyroid surgery for a definitive diagnosis and cure. The bottom line is thyroid nodule size is matters.

For more information regarding thyroid nodules and evaluation, see our article Top 5 Worries About Thyroid Nodules.

Figure 2: Thyroid nodule size chart demonstrates relative size and the effects large nodules have on the thyroid gland. Enlarged right thyroid lobe shown would lead to symptoms like difficulty breathing and swallowing and would require surgical treatment.

#2 Thing to Know About Thyroid Nodule Size: Thyroid Nodule Size Over 4 cm Requires Surgery

As noted above, thyroid nodules are common, occurring in 40% of women and 30% of men during their lifetime. Most nodules are benign, but even benign nodules can require surgery. Thyroid nodules are often diagnosed as benign by needle biopsy during a patient evaluation. Although these nodules are benign, almost all of them will enlarge or grow over time. Thus, thyroid nodule size is one reason for benign thyroid nodule surgery. Any nodule that is 4 cm or larger should be removed with thyroid surgery.

Like any tumor or growth elsewhere in the body (face, forehead, forearm, neck, etc.), you cannot let thyroid nodules continue to grow or enlarge forever. There is no reason to let a thyroid nodule continue to enlarge or grow past 4 cm. As these nodules get bigger, they can cause symptoms and the needle biopsies are less reliable (due to the increasing volume that cannot be completely sampled with a tiny needle). Eventually, the nodules will cause issues such as difficulty swallowing or breathing, a noticeable lump or mass in the neck, pressure/discomfort (particularly when laying down), and a feeling of a lump or something stuck in one’s throat. Additionally, as these nodules grow, they can extend into the chest cavity, or push on the windpipe (trachea) or swallowing tube (esophagus), or grow behind the voice box. As thyroid nodule size increases, so too does the likelihood of the symptoms mentioned above becoming noticeable. If thyroid nodule size reaches 4 cm, or your nodule is large enough to cause symptoms, then thyroid surgery for treatment is necessary.

#3 Thing to Know About Thyroid Nodule Size: Small Thyroid Nodules Can Be Scary

While most thyroid nodules are not cancerous as noted above, some are (5%, maybe 10%-15% at most). Thyroid nodule size does not correlate directly with the cancerous or benign nature of a thyroid tumor. All thyroid cancers start small, so just because a thyroid nodule is small does not mean it is benign. We have even seen rare cases where a small thyroid nodule (less than 1 cm) is a cancer that has spread to lymph nodes in the neck.

Any small nodule that is suspicious on an expert, high-resolution ultrasound should undergo evaluation with a needle biopsy, regardless of the thyroid nodule size. These smaller nodules are challenging to biopsy and this should only be done at high-volume centers such as ours. Patients should also realize that thyroid biopsies are only as good and reliable as the people performing them and the pathologists who are evaluating the cells. Frequently, a needle biopsy before surgery does not yield a definitive diagnosis as to whether a thyroid nodule is cancerous or benign (non-cancerous). Even special molecular genetic testing of thyroid cells from a biopsy often does not reveal whether a nodule is cancer or benign. As such, many thyroid nodules, particularly small ones, cannot be diagnosed as cancerous or benign until the entire nodule has been removed during thyroid nodule surgery where half or the whole thyroid is taken out. In some large studies, up to 50% of thyroid cancers are not diagnosed until after thyroid nodule surgery.

For more information about thyroid nodule surgery, please see our article Thyroid Nodule Removal: Top 4 Facts to Know.

#4 Thing to Know About Thyroid Nodule Size: Expert Thyroid Nodule Imaging is Important

The first imaging study used in work-up and evaluation of thyroid nodule size and any thyroid problem should always be an expert, skilled, dedicated thyroid and neck ultrasound. Thyroid ultrasound is the best and most common method for evaluating the thyroid. This imaging test uses sound waves to get pictures of the thyroid gland, surrounding tissue and structures, and the lymph nodes in the neck. This test exposes patients to absolutely no radiation. If your doctor first orders a CT scan, MRI, or PET/CT scan to evaluate your thyroid problems, you need a second opinion from an expert.

Thyroid ultrasound can help determine thyroid nodule size and whether the nodule is solid or filled with fluid. (Solid nodules are more likely to be cancerous.) This test can also be used to check the number of nodules, thyroid nodule size, and can even reveal what the blood supply to these nodules looks like. Additionally, this method is excellent to look for thyroid cancer that has spread to lymph nodes in the neck. Finally, ultrasound is also used to perform needle biopsies of thyroid lumps and lymph nodes to see if they are cancerous or not.

Thyroid Nodule Size: Summary

Thyroid nodules are very common. Thyroid nodule size is certainly important, but is not the only clinical factor that determines whether a biopsy, surgery, and/or surveillance is needed. Not all large nodules are bad, and not all small nodules are benign. Thyroid nodule surgery, involving removal of half or the whole thyroid, is often necessary to diagnose and cure these nodules, regardless of thyroid nodule size. Large nodules, symptomatic ones, nodules that are growing, and ones that are atypical or suspicious (on ultrasound or needle biopsy) often require thyroid nodule surgery. The first imaging test used in work-up and evaluation of thyroid nodule size and any thyroid problem should always be an expert, skilled, dedicated thyroid and neck ultrasound.

Expert evaluation and treatment for thyroid nodules are paramount. Our team of thyroid cancer experts is here to help and guide you every step along the way and will be there for you after your thyroid nodule surgery. To learn more and become a patient, please see our resources below.

Additional Resources

• Become our patient by filling out the form at this link. 
• Learn more about The Clayman Thyroid Center here. 
• Learn more about our sister surgeons at the Scarless Thyroid Surgery Center, Norman Parathyroid Center, and Carling Adrenal Center
• Learn more about the Hospital for Endocrine Surgery.