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Are Thyroid Nodules that Grow Cancerous?
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What is the problem and what is known about it so far?
The thyroid gland is located at the bottom of the neck. It makes hormones that help control the body's rate of metabolism (regular chemical processes of the body). Sometimes, the thyroid gland develops abnormal growths, often called nodules. The growths are usually small, and they can be solid or cystic (filled with fluid). Most nodules are benign, but some are cancerous. Doctors use blood tests, special scans, and needle aspiration to determine which growths are benign or cancerous. Benign nodules are followed closely because doctors typically regard nodules that increase in size as suspicious for malignancy. They often repeat needle aspiration of the nodules that increase in size to check for malignancy. However, whether change in size reliably identifies nodules that are cancerous has not been well studied.
Why did the researchers do this particular study?
To see whether benign thyroid nodules typically grow over time and whether change in size indicates cancer.
Who was studied?
268 patients with 330 benign thyroid nodules. The average age was 47 years, and 91% of patients were women.
How was the study done?
The researchers reviewed records of all patients who had been referred to a thyroid clinic between 1995 and 2000. They looked for patients with thyroid nodules (measuring 1 cm or greater in diameter) whose needle aspirations had shown no evidence of cancer and who had returned for follow-up at least once within the 5-year period. At follow-up visits, patients had repeat ultrasound scans of the thyroid to check for change in growth size. Doctors used their best judgments in deciding whether to repeat needle aspiration of the growths.
What did the researchers find?
The size of benign nodules typically increased over time. Most nodules (89%) increased in size by 15% or more after 5 years. Solid nodules grew more often than nodules with cysts. Doctors reaspirated 74 of the 330 nodules at follow-up visits. Despite an average increase in size of 69%, only 1 of the reaspirated nodules was cancerous.
What were the limitations of the study?
The study was retrospective and included only patients who returned for follow-up visits. Not all patients were monitored or followed in the same manner. Some patients with cancer may have been missed.
What are the implications of the study?
Benign thyroid nodules that have no evidence of cancer on initial needle aspiration typically grow over time. Increase in size does not reliably indicate cancer.
Article and Author Information
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The summary below is from the full report titled “Natural History of Benign Solid and Cystic Thyroid Nodules.” It is in the 18 February 2003 issue of Annals of Internal Medicine (volume 138, pages 315-318). The authors are EK Alexander, S Hurwitz, JP Heering, CB Benson, MC Frates, PM Doubilet, ES Cibas, PR Larsen, and E Marqusee.
- Copyright ©2004 by the American College of Physicians
