A Pain in the Neck

By Peter Galvin, MD

As you probably know, the thyroid gland is located in the front of the neck and is responsible for producing hormones that regulate metabolism. Thyroid cancer is diagnosed in about 44,000 people in the U.S. every year, and over the last four decades the number of those diagnosed with it has steadily increased. But the rate of thyroid cancer is rising because of advances in imaging technologies which allow us to visualize small cancers that heretofore were undetectable. Most patients with thyroid cancer, notwithstanding the title of this article, have no symptoms prior to diagnosis, and the five-year-survival rate after diagnosis of thyroid cancer is 98.5%.

The strongest risk factor for thyroid cancer is exposure to ionizing radiation in childhood, which may occur if the neck was exposed to radiation during treatment for lymphoma (including Hodgkin’s lymphoma) or acne (yes, radiation was once used to treat severe acne, starting in the 1950s). Thyroid cancers were commonly seen in the survivors of Hiroshima and Nagasaki, and also in those who lived downwind of Trinity, the A bomb test site in New Mexico. Thyroid cancer is also diagnosed more commonly in adults aged 60 and older, especially in women, and those with a family history of it.

Thyroid cancer has a very high long-term survival rate because about 84% of cases are the papillary type and are well differentiated (the cells appear orderly under a microscope). Only about 5% are poorly differentiated and 1% are anaplastic (under a microscope, the cells are a jumbled mess). As a general rule, the more orderly or well differentiated cancer cells appear, the less aggressive the tumor is. Approximately 4% of patients have medullary cancer, which has a significant genetic component. Thyroid cancer can be detected during a physical exam when the clinician detects a thyroid lump, but often it (a thyroid nodule) is found when an ultrasound, CT scan, or MRI of the neck is done for other reasons. In other words, it is often found by accident, which is called an incidental finding. Remember, thyroid cancer is almost always asymptomatic. Most thyroid nodules are not cancerous, but if the ultrasound exam has findings that may indicate malignancy (irregular borders, increased blood flow, or microcalcifications), a needle biopsy is indicated.

Surgical removal of the thyroid gland (thyroidectomy) can cure most patients with well differentiated thyroid cancer. After surgery, patients are monitored with thyroid blood tests (thyroid hormone medication is usually needed after thyroidectomy) and serial neck ultrasounds at intervals of about six to 12 months. Occasionally, someone with a very small (< 1.5 cm.) cancer may be monitored with serial ultrasounds instead of surgery. Treatment with radioactive iodine after surgery improves survival in patients at high risk for cancer recurrence. Also available are medications that inhibit blood vessel growth in cancers and medications that target cancer-promoting genetic mutations. Finally, inoperable cancers can be treated with radiation therapy.

The U.S. Preventive Services Task Force (USPSTF) recommends against routine screening for thyroid cancer because it is both cost-inefficient and unlikely to yield many positive results. For more information go to the website of the National Cancer Institute at www.cancer.gov

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