PHOENIX — Thyroid nodules found on clinical examination were much more likely to be malignant than were those seen incidentally during imaging studies for other reasons, according to a new review of 200 consecutive patients referred to a thyroid center.
The findings, which differ from those previously reported in the literature, were presented here at the American Association of Clinical Endocrinologists 2013 Scientific & Clinical Congress by Robert A. Levine, MD, and Jessica K. Levine.
"We have long known of a clear relation between nodule hardness and risk of malignancy. Since a hard nodule is easier to feel by the clinician or the patient, it would seem likely that the easily felt nodule may be more suspicious," Dr. Levine, medical director of the Thyroid Center of New Hampshire, Nashua, told Medscape Medical News.
The study results highlight the increasingly common conundrum of what to do with thyroid nodules identified during the course of imaging for other reasons, he said. Current guidelines call for biopsy of most nodules larger than 1 cm.
Thyroid nodules are an extremely common problem, with 4% of the population having a palpable nodule and more than 50% having a nodule detectable on high-resolution ultrasound. During the past 7 years, both the number of thyroid nodule biopsies performed in the United States and the diagnosis of thyroid cancer has doubled, to 450,000 and 57,000, respectively. Despite those increases, the death rate from thyroid cancer has remained relatively stable for several decades, at about 1500 per year.
The American Thyroid Association (ATA) is currently revising its recommendations regarding which nodules should be examined with biopsy and which can merely be monitored, said Dr. Levine, adding that the economic impact of evaluating all nonpalpable thyroid nodules is immense.
"We are hoping to see [new] guidelines for the incidentally found nodules, as the current recommendations are scant. I hope that endocrinologists and primary-care physicians will better appreciate the importance of physical examination as a means of finding the more suspicious nodules," he told Medscape Medical News.
Mode of Nodule Discovery Matters
Among the 200 scans reviewed, 33.5% of cases were found incidentally on imaging studies. Just over half of those were found on computed tomography (CT) scans of the chest; fewer were discovered with magnetic resonance imaging (MRI) and carotid ultrasonography. Another 37.5% were located on physical examination, and 12% were found by the patient.
The other 17% were identified during thyroid ultrasound examinations, many of which were performed because of abnormal results on thyroid-function tests, but in about half of these cases, there was no clear indication for the ultrasound.
Biopsies were performed in 141 (70%) of the 200 cases. The remaining 30% of nodules did not meet current guidelines for biopsy on the basis of size and ultrasound features.
Of the 141 for which biopsy was performed, 8.5% (12) were confirmed as cancer. Of those 12 cases, 7 were initially discovered during physical examination and 3 were found by the patient. Only 1 cancer was identified via referral for an abnormality seen on an imaging study. The remaining case was detected during an ultrasound evaluation for hyperparathyroidism.
Thus, 9% (7/75) of the nodules discovered during physical examination were malignant, compared with just 1.5% (1/67) of those found on imaging. The highest malignancy rate, 12.5%, was seen in nodules detected by the patients themselves (3/24).
These results differ from several previous reports, in which the rates of malignancy among incidentally discovered nodules ranged from 3.9% to 17%; this study's small sample size might explain the discrepancy, the researchers said.
For this reason, this study will be repeated in a larger patient population at a thyroid center in Sarasota, Florida, and in a thyroid clinic in a university-based medical center. Geographical differences in the mode of discovery of the nodules will also be explored, as will the impact of variations in referral patterns, Dr. Levine said.
Awaiting Guidelines to Ensure Proper Practice
Dr. Levine told Medscape Medical News that on CT imaging, cysts may appear more obvious than solid nodules, so CT may frequently show less suspicious, common, small cystic lesions.
"We need to be able to distinguish between a tiny, benign-looking cyst on a CT scan and an angry, calcified thyroid nodule with lots of lymph nodes in the neck."
His group is now looking into the comparison of CT and ultrasound appearance in attempts to correlate the 2 and to set up initial recommendations for what constitutes a worrisome finding on CT.
Once the new ATA recommendations become available, "We need to disseminate the guidelines regarding the proper utilization of thyroid ultrasound to primary-care providers so we don't get people being referred for an imaging study when they presented with a 2-day sore throat or a mildly abnormal thyroid-function test," he concluded.
Neither of the authors has disclosed any relevant financial relationships.
American Association of Clinical Endocrinologists (AACE) 22nd Annual Scientific and Clinical Congress. Abstract 1048, presented in a poster on May 2 and at a press briefing on May 3, 2013.