CHICAGO — Although only 4%–8% of adults have palpable thyroid nodules, as many as 10%–50% of adults will have nodules whose presence is confirmed by ultrasound, Dr. Roberta M. diFlorio of Dartmouth Medical Center in Hitchcock, N.H., reported at the annual meeting of the Radiological Society of North America.
Nodules are also found incidentally on CT and MRI scans in 4%–16% of patients, according to Dr. diFlorio, assistant professor of radiology at Dartmouth. Autopsy studies have found even higher rates of thyroid nodules—30%–60%, she added.
To better understand radiology practice patterns for thyroid nodule management, Dr. diFlorio sent surveys to 106 Society of Radiologists in Ultrasound fellows in 2005. She received 50 responses (a 47% response rate) from 42 institutions.
One issue that especially interested Dr. diFlorio was the frequency with which radiology departments performed fine-needle aspiration (FNA) procedures to rule out malignant nodules. “This is the most common procedure we do in our department,” she noted.
To attempt to reduce the number of unnecessary thyroid biopsies and FNAs, the Society of Radiologists in Ultrasound released guidelines for managing thyroid nodules in 2005. The management recommendations were based on the size, shape, and character of the nodules as seen on ultrasound.
The survey found that most responding institutions (28) performed more than five thyroid aspirations per week. The ultrasound feature that most commonly triggered an aspiration was size, with 22 respondents reporting that the presence of a nodule greater than 1 cm on ultrasound would lead to an FNA. (Respondents could indicate that more than one ultrasound feature triggered an FNA.)
Thirteen respondents said that a dominant nodule would lead to an FNA, and 11 respondents said that a cold nodule would be a criterion for an FNA. Overall, 20% of respondents said that they routinely sample more than one nodule.
Despite the high prevalence of thyroid nodules, cancer rates remain low. About 5%–10% of palpable nodules are malignant, and similar malignancy rates—5%–13%–-have been found for nodules seen on ultrasound, Dr. diFlorio said.
Only about half of the respondents (22) reported that cells for cytology were routinely present in the aspirate.
Overall, the respondents confirmed that FNAs lead to a relatively low diagnostic yield for thyroid cancer, with 29 respondents reporting that 0%–10% of the FNA procedures are diagnostic, 11 respondents saying that 10%–20% of the procedures are diagnostic, and only 2 respondents indicating that more than 20% of the procedures lead to a diagnosis.