Triage of the indeterminate thyroid aspirate: What are the options for the practicing cytopathologist?

Fine-needle aspiration (FNA) plays a key role in the early evaluation of patients with thyroid nodules; however, from 15% to 30% of FNA specimens are cytologically indeterminate. Molecular testing has proven useful when applied to indeterminate thyroid FNAs, and its use has been endorsed in the American Thyroid Association guidelines. In addition to the noncommercial ("in-house") application of v-Raf murine sarcoma viral oncogene homolog B1 (BRAF), rat sarcoma (RAS), rearranged in transformation/papillary thyroid carcinoma (RET/PTC), and peroxisome proliferator-activated receptor γ/paired box gene 8 (PPARγ/PAX8) testing, there are currently 3 commercially available molecular panels that vary in their relative reported performances, strengths, and limitations. Here, we discuss the role of molecular testing for indeterminate thyroid aspirates, taking into consideration the recent reclassification of the encapsulated follicular variant of papillary thyroid carcinoma (PTC) as "noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP)." Cancer Cytopathol 2017;125(6 suppl):477-85. © 2017 American Cancer Society.