Risk of malignancy and neoplasia predicted by three molecular testing platforms in indeterminate thyroid nodules on...

The management of thyroid nodules with indeterminate cytology is challenging. Recently, molecular testing on fine-needle aspirates (FNAs) has been advocated to determine whether clinical follow-up or surgery is warranted for patients. Three different testing platforms were performed on aspirates from our institution (Afirma Thyroid FNA Analysis, RosettaGX Reveal, and Interpace ThyGenX/ThyraMIR). This study compares their diagnostic efficacy.

We conducted a retrospective analysis of indeterminate thyroid FNAs with correlating molecular testing over 4 years (2015-2018). The aspirates included diagnoses of follicular lesion of undetermined significance, follicular neoplasm, or suspicious for malignancy (SM). Based on cases that underwent surgical resection (Afirma, n = 37; Rosetta, n = 19; Interpace, n = 14), we calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for risk of malignancy and neoplasia.

The three tests performed similarly when predicting risk of malignancy. They showed high sensitivity (80-100%) and NPV (90-100%) but lower specificity (10-64%) and PPV (21-44%). When assessing their value to predict neoplasia, each test had a high PPV (76-89%) but low NPV (20-33%). The sensitivity for neoplasm was intermediate to high (50-93%), and the specificity remained extremely variable (11-67%).

Overall, these molecular platforms performed similarly, displaying high NPV but low to intermediate PPV for malignancy and low NPV but high PPV for neoplasm. The risk of neoplasm is a good index for surgery, and we argue that many of the neoplasms are low-risk tumors. We endorse conservative treatment with lobectomy for cases that are indeterminate at FNA but suspicious by molecular testing.