DENVER (FRONTLINE MEDICAL NEWS) – The malignancy risk of thyroid nodules can be assessed with reassuring accuracy using ultrasound and the guidelines developed by the American Thyroid Association.

Ultrasound assessment is the first step of the evaluation of any patient with one or more thyroid nodules. “Maybe it shouldn’t be, but, for now, it is,” noted David L. Steward, MD , at the annual meeting of the American Thyroid Association.

In this prospective study, Dr. Steward, professor of otolaryngology at the University of Cincinnati, and his associates used ultrasound to assess 211 thyroid nodules in 199 patients (157 women) over the course of 14 months. The nodules that looked to be of high risk of malignancy, intermediate risk, low risk, or very low risk first underwent fine needle biopsy and, based on those results, were biopsied or sometimes excised. The pathologists then used the Bethesda System for Reporting Thyroid Cytopathology to evaluate the samples.

The ATA guidelines categorize thyroid nodules on the basis of their ultrasound patterns, with the high risk of malignancy being in nodules that are taller than they are wide and /or have microcalcifications, irregular margins, hypoechoic areas, extrathyroidal extension, interrupted rim calcification with soft tissue extrusion, and suspicious lymph nodes. Between 70% and 90% of thyroids with such patterns will contain malignancy, according to the ATA guidelines. Lesions with an intermediate risk of malignancy have such sonographic findings as hypoechoic solid tissue and regular margins; between 10% and 20% of these are malignant. The third category in the ATA’s guidelines are those that are of low suspicion, with hyperechoic solid tissue, isoechoic solid tissue, partially cystic with eccentric solid area, and regular margins; 5%-10% of these are malignant. Thyroid nodules with a very-low risk of malignancy (less than 3%) are spongiform or partially cystic with no suspicious findings. Finally, benign nodules, of which less than 1% contain malignancy, are cysts, he said.

“We found that the size of the nodule on ultrasound that underwent fine needle aspiration was inversely correlated with malignancy risk: The lower risk nodules were larger,” he said.

Using the ATA’s system, 9 (4%) of the nodules were high risk, 64 (31%) were intermediate risk, 79 (38%) were low risk, 54 (26%) were very-low risk, and none were benign. Five of the nodules were not included in the results presented.

There was good correlation between the Bethesda and ATA classification systems. Of the lesions that were malignant or suspicious for malignancy in the Bethesda system, 77% were very-high risk for malignancy on ultrasound according to the ATA. Of the lesions that were atypia of undetermined significance (AUS)/follicular lesion of undetermined significance (FLUS), 22% were very high risk according to the ATA. Neither of the systems classified as malignant any of the lesions as follicular/Hurthle cell cancer, benign, or nondiagnostic.

The AUS/FLUS nodules “tend to be all over the map,” he noted. Looking at just the AUS/FLUS nodules, malignancy was found on pathology in 100% classified by the ATA system as being high risk; in 21% of those called intermediate risk; in 17% of those called low risk; and in 12% of the very-low risk group.

The study was funded by the University of Cincinnati. Dr. Steward said his only disclosure is that he was a member of the ATA committee that wrote the guidelines under evaluation in this study.