WASHINGTON — The decision to perform fine-needle aspiration on a patient with a thyroid nodule depends on several factors, including nodule size, serum thyroid stimulating hormone level, and presenting symptoms, Dr. Erik Alexander said at a meeting jointly sponsored by the American Thyroid Association and Johns Hopkins University.
Dr. Alexander, who is with the division of endocrinology, diabetes, and hypertension at Brigham and Women's Hospital in Boston, outlined the algorithm he uses to evaluate a thyroid nodule.
Male gender, young age, and being symptomatic can increase the risk of a nodule being cancerous by about twofold, he said. But even if a nodule turns out to be cancerous, it doesn't necessarily mean that something has to be done about it.
“Do all thyroid cancers pose a danger? I think the answer likely is no,” said Dr. Alexander, who is also an assistant professor of medicine at Harvard Medical School, Boston. “Nodules that are over 1 cm are really the nodules and cancers that pose risk” because of their increased likelihood of distant metastasis.
One recent 10-year study of 650 patients with well-differentiated follicular or papillary thyroid carcinoma found that with papillary thyroid carcinoma, there was essentially a zero risk of extrathyroidal growth in cancers of 10 mm or less in diameter, further validating the idea of a 1-cm cutoff, Dr. Alexander said (Cancer 2005;103:2269–73).
Ultrasound imaging can help further determine the risk of a nodule being cancerous, but cannot rule out the need for fine-needle aspiration, Dr. Alexander noted. That's because several studies have shown that ultrasound identifies only about 80% of thyroid cancers. “Would any of us be willing to have a 20% false- negative rate? I don't think so.”
On the other hand, “Ultrasound is highly useful; it's most effective at assessing cancer risk,” he continued.
One study done at Dr. Alexander's hospital found that a woman who presents with a solitary nodule that is found on ultrasound to be completely solid with punctate calcifications has a 33% chance of that nodule being cancerous, while a woman who presents with a multiple nodules found on ultrasound to be mixed solid and cystic with rim or coarse calcifications has a much lower risk—about 6% (J. Clin. Endocrino. Metab. 2006;91:3411–7).
Dr. Alexander's approach to assessing thyroid nodules begins with a thyroid ultrasound. If no nodules greater than 1 cm are found, no more intervention is warranted. If a nodule greater than 1 cm is found, he orders a serum TSH test. If TSH is suppressed, he orders a thyroid scan to look for a toxic adenoma; if it is normal or elevated, he considers whether the patient is symptomatic or not.
In symptomatic patients, he performs fine-needle aspiration; for asymptomatic patients, he assesses their cancer risk—as determined by gender, ultrasound results, and serum TSH—as well as their comorbidities and, in an older population, estimated longevity, before deciding whether to proceed with aspiration.
He noted that 70% of nodules evaluated by fine-needle aspiration prove benign. And although Dr. Alexander's protocol puts the question of fine-needle aspiration at the end of the evaluation, “there are some individuals in which [an earlier] fine-needle aspiration would be helpful in giving you further data,” he said, adding that “fine-needle aspiration does not obligate you to further intervention,” even if suspicious or intermediate lesions are found.