ThyroSeq overview on indeterminate thyroid nodules: An institutional experience

Background

Molecular triage of indeterminate thyroid aspirates offers the opportunity to stratify the risk of malignancy (ROM) more accurately. Here we examine our experience with ThyroSeq v3 testing.

Methods

We analyzed 276 of 658 (42%) fine needle aspiration samples classified as indeterminate thyroid nodules using ThyroSeq v3 (Sept 2017–Dec 2019). The test provides a ROM and detects specific mutations. Surgical diagnoses were reviewed.

Results

Of 276 ThyroSeq-tested cases, 42% (n = 116) harbored genetic alterations, whereas 64% (n = 74) had surgical follow-up. Notably, 79% cases within intermediate to higher risk mutations were highly associated with surgical intervention, resulting in a 77.5% ROM when including both cancer and noninvasive follicular thyroid neoplasia with papillary-like features (cancer+NIFTP) and 68% malignant diagnosis when excluding NIFTP. RAS-like alterations were most common (66%), exhibiting a 73.4% ROM and a 59% malignant diagnosis. Interestingly, this group included 24 encapsulated follicular variant papillary thyroid carcinomas (EFVPTCs), 1 infiltrative FVPTC, 9 follicular carcinomas, and 7 NIFTP. Additionally, three high-risk mutations and eight BRAF/V600E mutations had a 100% ROM, all diagnosed as classic-type papillary thyroid carcinoma (cPTC). Combined analysis of thyroid nodules from Bethesda III and IV categories revealed a 78.2% positive predictive value (PPV) and a 75.9% negative predictive value (NPV).

Conclusion

ThyroSeq v3 effectively stratifies the ROM in indeterminate thyroid nodules based on specific genetic alterations, guiding appropriate surgical management. Notably, the BRAFV600E/high-risk group and RAS-like groups exhibited ROM of 100% and 77.5%, respectively, with promising predictive accuracy (PPV of 78.2% and NPV of 75.9%).