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Thyroid Diseases

Rapidly Growing Thyroid Nodule and Cancer Risk

01/09/2007

Question:

I would like to know what defines a "rapidly growing" thyroid nodule? I have a thyroid nodule in the right lobe of my thyroid. My initial ultrasound six months ago showed it measuring 3 cm x 1.8 cm x 1.8 cm. My most recent ultrasound taken three days ago, showed that my nodule is now approx 3.27 cm x 2.3 cm x 2.1 cm. Would this be considered "rapid growth"?

My initial biopsy results were benign. I have a follow-up appt in about two weeks with my endocrinologist. Should I expect another biopsy? If the nodule should continue to grow at this rate during the next six months, would that indicate surgery to remove the nodule? I have no other symptoms besides large nodule (not fluid filled).

Answer:

The fact that the initial biopsy was benign is very reassuring. Only about 2-5% of nodules felt to be benign by needle aspiration biopsy will eventually turn out to be cancers. Thyroid cancer is such a slow-growing cancer and usually responds so well to treatment that 2-5% is a very acceptable rate of initially missing thyroid cancers (the alternative would be to send everyone with thyroid nodules to surgery - a strategy that the experts feel is unnecessary).

Benign nodules can grow, so the fact that the nodule is slowly growing is not especially worrisome. Still, according to the American Thyroid Association guidelines, thyroid nodules that grow should be re-biopsied to be sure that a cancer hasn't been missed. There is disagreement as to how much growth warrants re-biopsy. The American Thyroid Association guidelines suggest that it is reasonable to re-biopsy a nodule if the diameter grows by 20% with a minimum increase in two or more dimensions of at least two mm (0.2 cm). However, this is not an absolute rule, and you should probably leave it up to your doctor to decide when re-biopsy is indicated.

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Response by:

Thomas A Murphy, MD, FACP, FACE Thomas A Murphy, MD, FACP, FACE
Associate Professor of Medicine
School of Medicine
Case Western Reserve University