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DEAR MAYO CLINIC: During a routine physical exam recently, my health specialist said she felt a thyroid nodule. I was told I'd need to have it checked, but I am concerned this might be cancer. What workup and treatment do I need?
ANSWER: The thyroid gland is an organ in the neck that is responsible for making hormones which regulate many different aspects of metabolism and are essential for normal health. It is quite common for people to develop thyroid nodules — about half the population in the U.S. are estimated to have a nodule by the time they are 60. The thyroid is routinely assessed during routine medical exams. Sometimes, patients feel the nodules themselves or have symptoms that bring the nodules to their health care team’s attention. Fortunately, most nodules are benign, but a workup is necessary to determine whether there may be thyroid cancer present.
Evaluation of a suspected thyroid nodule begins with understanding the risk of developing thyroid cancer based on your personal situation and other medical conditions. Your health care professional will ask whether other members of your family have thyroid cancer and about exposures that may increase the risk of developing thyroid cancer, such as having received high levels of radiation in the past. The next step is to proceed with testing.
Testing generally will include checking how much thyroid hormone is being produced by measuring thyroid stimulating hormone, or TSH, in the blood and imaging the thyroid gland with an ultrasound. Most thyroid nodules will appear benign by ultrasound, and if small and otherwise asymptomatic, may not require any further workup. Some thyroid nodules will appear more concerning. Cancerous nodules tend be irregular, larger, grow over time, may have calcifications, and may appear darker than the surrounding normal thyroid. The ultrasound characteristics, as well as the size of the nodule, will determine whether proceeding with biopsy is warranted.
If a biopsy is recommended, this usually is performed using fine needle aspiration, which can be performed in the clinic setting. This technique uses a small needle to obtain cells from the nodule, which are then reviewed by a cytopathologist. Most biopsies will be reported by the cytopathologist as benign. However, some biopsies will show a cancer is present, or that there are indeterminant features, which means a cancer might be present. Papillary thyroid carcinoma is the most common thyroid cancer diagnosed. It is also generally the least dangerous thyroid cancer to have.
If a cancer is suspected or confirmed by fine needle aspiration biopsy, then a discussion proceeds to treatment planning.
The first step in managing most thyroid cancers is surgical resection. Preoperative ultrasound should include a comprehensive evaluation of the lymph nodes in the neck — both around the thyroid, which is in the central neck, and out to the sides of the neck — to evaluate for possible spread of cancer to lymph nodes. If any lymph nodes appear worrisome, additional biopsies can be performed to confirm spread, or metastasis. This is important to know about prior to surgery because metastatic cancer requires more extensive surgery.
Surgery for thyroid cancer may include removal of the entire thyroid, called a total thyroidectomy, or, in many cases, removal of only the portion of the thyroid that contains the thyroid cancer, known as a thyroid lobectomy. Small cancers that do not appear to have spread outside of the thyroid commonly are managed with thyroid lobectomy, while larger cancers or cancers where there is concern for metastasis are more likely to be treated with total thyroidectomy.
Many cases of thyroid cancer are completely treated with surgical excision. However, some patients will be advised to also undergo radioactive iodine therapy, which can help treat thyroid cancer that has spread outside of the thyroid and help make surveillance for recurrent thyroid cancer easier. At Mayo Clinic, patients work closely with an endocrinologist and surgeon in a collaborative fashion to determine the extent of surgery to perform and to decide whether treatment with radioactive iodine therapy after surgery is necessary.
In summary, thyroid nodules are common and most are benign. Workup for thyroid cancer typically involves ultrasound evaluation and possible biopsy. If thyroid cancer is confirmed, referral to surgery is often the next step. Thyroid surgery can be curative for many cases of thyroid cancer and is able to be performed with low risk of complications in the hands of experienced surgeons. Each situation is unique, so it is important to have an experienced, multidisciplinary team of experts conduct the workup for thyroid cancer and provide the cancer treatment to ensure the best possible outcome. — Dr. Trenton Foster, Surgery, Mayo Clinic, Rochester, Minnesota