The thyroid gland is a butterfly-shaped structure situated in the lower part of the neck. The thyroid gland is important because it produces the thyroid hormones T4 and T3 which regulate the metabolic functions of the body. These hormones affect all the parts of the body and control the pace at which every cell in the body functions.
Two common types of problems can affect the thyroid gland
- Development of nodules/lumps/growths or swellings
- Non-cancerous (Benign)
- Cancerous (Malignant)
- Changes in the function of the gland
- Decreased thyroid hormones (hypothyroidism)
- Increased thyroid hormones (hyperthyroidism)
Thyroid nodules are a common problem affecting this gland. These nodules are solid or fluid filled lumps that form within the thyroid gland. An enlarged thyroid gland due to any cause is called a goiter. A thyroid nodule may present as a swelling in the neck or maybe incidentally detected when a scan is performed for other reasons. Thyroid nodules become more common as a person becomes older, and can be present in 18.0 and 14.5 percent in women and men over the age of 55 years. Fortunately, about 90% of thyroid nodules are generally benign (not cancer).
Some common causes of thyroid nodules are:
- Benign multinodular goiter
- Toxic multinodular goiter
- Colloid cyst
- Toxic adenoma
- Benign follicular neoplasm
- Thyroid cancer
What are the symptoms associated with thyroid nodules?
Thyroid nodules are frequently asymptomatic and are usually found during a routine examination of the neck by a health care provider. Occasionally, however, some nodules become so large that they can be seen easily, or can press on the windpipe or esophagus causing breathing or swallowing difficulty. In some cases, thyroid nodules produce additional thyroxine, a hormone secreted by the thyroid gland. The extra thyroxine can cause symptoms of hyperthyroidism such as weight loss, sweating, tremor, and irregular heartbeat. Treatment options depend on the type of thyroid nodule.
How are thyroid nodules evaluated?
A few thyroid nodules are cancerous (malignant), but determining which nodules are malignant can’t be done by symptoms alone. Most cancerous thyroid nodules are slow-growing and maybe small when they’re discovered. Aggressive thyroid cancers are rare, but these nodules may be large, firm, fixed and rapid growing. Although the chances that a nodule is malignant are small, certain factors point to a higher risk of malignancy.
Risk factors which may point to a nodule being cancer include:
- Family history of thyroid cancer
- A nodule that is hard or is stuck to a nearby structure
- Male gender
- Age younger than 20 and older than 60
- Radiation exposure
- Nodule with a sudden increase in size
- New onset of symptoms like change in voice, difficulty in breathing or difficulty in swallowing
When do you need to see a doctor for your thyroid swelling?
Although most thyroid nodules are noncancerous (benign) and don’t cause problems, ask your doctor to evaluate any unusual swelling in your neck, especially if you have trouble breathing or swallowing. It’s important to evaluate the possibility of cancer if you notice an increase in the size of the swelling.
Also seek medical care especially if you develop signs and symptoms of hyperthyroidism, such as weight loss, weakness, palpitation or tremors.
It is, however, prudent to have an initial evaluation done, for all thyroid nodules. If initial investigations are indicative of a benign (non-cancerous) swelling, you can plan for regular follow-up as suggested by your doctor.
What are the tests done for the evaluation of thyroid nodules?
Your doctor will evaluate your nodule in order to answer four key questions
- Is the nodule cancerous?
- Is the nodule causing trouble by pressing on other structures in the neck?
- Is the nodule making too much thyroid hormone?
- Do you need to do anything about your thyroid nodule?
Three important categories of tests that will be ordered by your doctor are:
- Thyroid function tests – These are blood tests to determine the level of thyroid hormone in your body. Thyroid nodules rarely produce too much thyroid hormone. But when excessive thyroid hormone is being produced by the thyroid nodule this is almost always associated with a benign (non-cancerous) nodule. Benign thyroid nodules that produce extra thyroid hormone are usually removed to cure excessive hormone production. Most thyroid nodules will, however, be nonfunctional and will not change your TSH, T4 or T3 levels.
- Ultrasound of the thyroid -The second test which is performed in the evaluation of a thyroid nodule is an ultrasound. This imaging technique uses high-frequency sound waves to produce images. It provides the best information about the shape, extent, and structure of the nodule. Ultrasound of the neck includes analysis of the neck lymph nodes as well. Because thyroid cancers can frequently spread to neck lymph nodes, the ultrasound analysis of the neck provides important information about a probable cancerous nodule. The ultrasound is valuable in looking for high-risk features in a thyroid nodule. We follow the TIRADS classification for thyroid nodules to assess the risk of cancer.
- Fine Needle Aspiration Cytology (FNAC) – FNAC is done to look for cancer cells in a nodule. It helps to distinguish between benign and malignant thyroid nodules. During the procedure, your doctor inserts a very thin needle in the nodule and removes a sample of cells.
FNAC is usually considered for nodules that are greater than 1 cm in diameter. Smaller nodules are generally not biopsied unless other concerning findings are noted. Cytopathologists grade the nodule by looking at the cells through a microscope. This technique can help to determine whether a nodule is benign or cancerous. However in many cases, the appearance of the cells can fall in between a benign and malignant diagnosis and are called indeterminate.
Additionally, any decision about treatment is not based only on FNAC as it is not a fool proof test.
Risk of cancer in FNAC of the thyroid
|Bethesda Class||FNAC category||Cancer risk|
|I||Inadequate||5 to 10%|
|III||Atypia of undetermined significance (AUS)/ Follicular lesion of undetermined significance (FLUS)||10-30%|
|IV||Follicular Neoplasm (or suspicious of follicular neoplasm)||25 to 40%|
|V||Suspicious of Cancer||50 to 75%|
|VI||Proven Cancer||97 to 99%|
Cibas ES, Ali SZ. The 2017 Bethesda system for reporting thyroid cytopathology.
Thyroid 2017; 27: 1341.
4.CT scan (computer tomography) of the neck – indications for CT scan are:
- Patients with very large swelling
- Large thyroid cancer with suspicion of invasion to adjacent organs
- Thyroid swelling going into the chest
- Medullary carcinoma of thyroid with calcitonin values > 500pg/ml.
Treatment of thyroid nodule
Treatment options depend on whether your nodule is benign or cancerous, and on the symptoms caused by the nodule.
Benign (non cancerous) nodule
If a thyroid nodule is definitely non cancerous, a number of treatment options can be considered, such as
- Watchful waiting and follow-upIf your FNAC shows benign features, your doctor may choose to keep you on regular check-ups with yearly clinical examination and ultrasound. You may need a repeat FNAC later on if your nodule grows in size. No further treatment may be needed if the nodule remains unchanged. If it is a purely cystic nodule alcohol ablation can be tried.
- Anti thyroid medication or radioactive iodineIf your thyroid nodule is found to be producing excessive amounts of thyroid hormone, your doctor may advise treatment with medication or radioactive iodine. Surgery to remove the toxic nodule is considered in patients for whom radioactive iodine or long term medications are not good options.
- Surgery– Indications for surgery in a patient with thyroid nodules include the following
- FNAC report showing cancer or suspicious of cancer
- FNAC report showing follicular neoplasm or atypia of undetermined significance
- Compressive symptoms
- Tightness in the neck
- Choking sensation
- Difficulty in swallowing or breathing
- Sticking sensation in the throat
- Deviation of your windpipe
- Cosmesis – undesirable appearance of a visible swelling
- Nodule extending into your chest (Retrosternal goiter)
- Size of the nodule > 4cm
- Surgical removal of the thyroid nodule is required if your nodule is found to be cancerous. Surgery is also advised for large nodules which can obstruct adjacent structures such as the windpipe and the esophagus. Nodules which have suspicious features with an unclear picture on FNAC may also need to be surgically removed.