Are the anatomical, clinical, and ultrasound characteristics of thyroid nodules with Bethesda III or IV cytology and ACR TI-RADS 3, 4, or 5 able to refine the indications for molecular diagnostic tests?

ABSTRACT Objective: To analyze the association of clinical, anatomical, and ultrasound (US) characteristics of malignancies in Bethesda III or IV (III-B or IV-B) thyroid nodules. Subjects and methods: The association between malignancies and the following variables were analyzed: III-B or IV-B, age < 55 years and ≥ 55 years, sex, family history of thyroid cancer, history of irradiation, nodule size, and ACR TI-RADS classification in 62 participants who underwent thyroidectomy. Results: Of the 62 participants, 87.1% (54/62) were women, 74.2% were < 55 years old, 95.2% had no family history of thyroid cancer, 56.5% had nodules < 2 cm in size, 62.9% were IV-B, and 69.4% were ACR TI-RADS 4. Thirty-two patients had thyroid carcinoma, and 30 had benign histology. Among all factors associated with malignancy, only ACR TI-RADS 5 classification on US was found to be statistically significant (p = 0.014), while III-B with architectural atypia cytological classification was the only one significantly associated with benign status (p = 0.004). Conclusion: Only a high risk of malignancy as assessed using US was able to refine the indication for molecular tests in a group of patients with indeterminate nodules. We found 85% (53/62) of III-B or IV-B thyroid nodules would benefit from available molecular diagnostic tests.

Molecular Testing of Thyroid Indeterminate Nodules for Clinical Management Decision

Thyroid nodules are the most common endocrine tumor. Ultrasonography and fine-needle aspiration (FNA) are currently accurate diagnostic tools for evaluating thyroid nodules. However, 10–30% of FNA specimens are cytologically indeterminate. Making an accurate diagnosis between benign and malignant nodules is important so that patients with malignant nodule receive proper treatment and patients with benign nodule can avoid unnecessary treatment. Several genetic changes such as point mutations of the BRAF or RAS and rearrangements of the RET/PTC1, RET/PTC3, PAX8/PPARY are used to adjust to indeterminate FNA. Such a mutational analysis has an excellent positive predictive value (PPV), but there is a weakness in the low negative predictive value (NPV). Gene-expression classifier (GEC) has been found helpful in identify nodules that are benign rather than malignant. GEC has an excellent NPV, but there is a weakness of low PPV. Multiplatform mutational and miRNA test (MPT) and next-generation sequencing assay (NGS) are being studied to compensate for these weaknesses. Molecular tests appear to be a good solution for improving the accuracy of indeterminate FNA cytology specimens and support the clinical management decisions in patients with indeterminate cytologic nodules, but further prospective multicenter trials are required for validation of reported findings and need evaluation of cost-effectiveness. This paper will review recently available molecular diagnostic tools of thyroid nodule.