The thyroid is a gland in the lower part of the front of the neck. It produces a hormone called thyroid hormone, which is involved in controlling your body’s metabolism. Nodules are small growths that can occur within the gland. These are very common and are usually benign. Nodules may be small or large, and there may be one or many of them within the gland.
While most thyroid nodules are benign, some may contain thyroid cancer. In order to determine if a nodule may be cancerous, a biopsy is done using a small needle. The is called a fine needle aspiration biopsy, or FNA. It is a simple procedure that takes only a few minutes and is typically done using the ultrasound machine to guide the needle into the nodule. The results of the FNA will come back described in a number of ways. It may be clearly benign in which case the nodule can be left alone. It may be found to be cancerous, in which case it must be removed with surgery. It is also possible that the FNA is “indeterminate.” This means that, for a variety of reasons, it cannot be determined definitively if the nodule is benign or malignant. There are additional tests, called molecular genetic tests, that are then performed on these indeterminate nodules. Often a clear diagnosis, benign or malignant, can then be determined on the basis of this further testing. It often takes an additional week to get these results. However, sometimes even after the molecular genetic analysis, the results are unclear. These nodules are considered suspicious, and surgical removal is recommended to determine if they are cancerous.
Benign nodules do not require surgical removal. Millions of people live with benign nodules that are not bothering them. Typically, we would monitor the nodule, or nodules, with yearly ultrasounds. A repeat biopsy may be recommended only if there is rapid change in the size. As a nodule or nodules grow, they may become bothersome. A nodule that reaches 4 to 5 cm will usually become noticeable to the patient. They may feel a sense of fullness in the neck. They may develop trouble swallowing or breathing. As the gland grows in size it may become cosmetically undesirable, as a visible mass in the front of the neck. An enlarged thyroid gland may also extend down beneath the collar bone or sternum into the chest. There, it may push on, or compress, the trachea. In these circumstances it may be beneficial to remove the thyroid even though the nodules are benign.
Interestingly, the presence of nodules in the thyroid gland is usually unrelated to the function of the gland. The thyroid gland may function completely normally despite having nodules. Conversely, your thyroid gland may be under or over-active, even if you do not have nodules within the gland. The functional status of the gland is determined by blood tests. The results of these blood tests do not tell us anything about the nature of the nodule, whether it is benign of malignant.
There is one uncommon exception, called a “hot” nodule. A hot nodule is a nodule that produces excessive amounts of thyroid hormone, causing the thyroid levels to be elevated, so called hyperthyroidism. Symptoms of hyperthyroidism include anxiety, heart palpitations, sweating, feeling hot, etc. It is as if your body’s thermostat is turned up too high. Hot nodules are almost always benign. They can be treated by surgical removal, a medication to lower the thyroid levels, or with a medication called radioactive iodine (RAI). RAI is iodine that has been made radio-active and given in pill form. The thyroid gland takes up iodine from the blood stream and uses it to produce thyroid hormone. No other tissue in the body takes up significant amounts of iodine, so the radioactive iodine is delivered selectively to thyroid cells. In this way the hyperactive nodule can be destroyed by the radiation. RAI is also used after surgery in some patients with thyroid cancers in order to kill off any microscopic thyroid cells that may be left behind or hidden in lymph nodes.
Not all thyroid nodules need to be biopsied. There are guidelines to help determine which nodules need to be biopsied and which can be simply observed. You can find these on the web site for the American Thyroid Association (ATA). What follows is a summary, rather than an exact reproduction, of the basic principles conveyed in the ATA guidelines. In almost all cases, nodules under 1cm in size should not be biopsied, they should simply be monitored with yearly ultrasounds. Nodules between 1 and 2 cm can either be biopsied or followed, depending on their appearance. There are certain characteristics of the nodule, beyond just the size, that can be seen on the ultrasound and can be either reassuring or concerning. Things such as: nodule shape, color, and texture, the appearance of the border of the nodule, is it smooth or irregular, are there calcifications within it, etc. These, and other characteristics, can determine the need for biopsy between 1 and 2 cm. Most nodules over 2cm should be biopsied. An assessment of the lymph nodes in the neck should be part of the ultrasound, and suspicious lymph nodes should be considered for biopsy as well.