A gene expression test may be able to differentiate patients who have benign thyroid nodules from those with malignant ones, reports a team led by Brigham and Women's Hospital researchers in the New England Journal of Medicine. Whether or not a thyroid nodule is benign or malignant can usually be determined by examining cellular morphological features from fine-needle aspiration samples, but the researchers say that about 15 percent to 30 percent of findings are indeterminate and patients with those findings often undergo surgery, possibly exposing them to unnecessary risk of surgical complications if their nodule was benign.

In NEJM, the researchers present the results of their validation trial of a gene-expression classifier for benign and malignant nodules. The classifier is made by Veracyte, which supported the study and has employees as co-authors. The classifier was used to test 265 indeterminate nodules, 85 of which were malignant, and the researchers report that the classifier was able to identify 78 of those 85 nodules as suspicious. Additionally, the negative predictive values for the three subtypes of indeterminate nodules — atypia or follicular lesion of undetermined clinical significance, follicular neoplasm or lesion suspicious for follicular neoplasm, or suspicious for malignancy — were, respectively, 95 percent, 94 percent, and 85 percent.

"This study shows that a gene-expression classifier can be used to identify a subpopulation of patients with a low likelihood of cancer in a population of patients for whom diagnostic surgery is otherwise recommended," the researchers write. "Though each clinical decision must be individualized, these data suggest consideration of a more conservative clinical approach for patients who have nodules with indeterminate cytologic features on fine-needle aspiration and a benign result on gene-expression classifier testing."