[Next generation sequencing]

Fine needle aspiration is the gold standard method to differentiate benign thyroid nodules from malignant. However, for 15 to 30% of the cases the cytological diagnosis is indeterminate, leading to surgery. Integration of new molecular markers is opening new perspectives in order to increase the diagnostic precision of thyroid nodules with an indeterminate cytology.

Next-generation sequencing improves the diagnosis of thyroid FNA specimens with indeterminate cytology

AIMS

The assessment of thyroid nodules is a common clinical challenge. Fine-needle aspiration (FNA) is the standard pre-operative tool for thyroid nodule diagnosis. However, up to 30% of the samples are classified as indeterminate. This often leads to unnecessary surgery. In this study, we evaluated the added value of next-generation sequencing (NGS) for helping in the diagnosis of FNA samples.

METHODS AND RESULTS

We analysed retrospectively 34 indeterminate FNA samples for which surgical resection was performed. DNA was obtained from cell blocks or from stained smears and subjected to NGS to analyse mutations in 50 genes. Mutations in BRAF, NRAS, KRAS and PTEN, that are known to be involved in thyroid cancer biology, were detected in seven FNA samples. The presence of a mutation in these genes was a strong indicator of cancer because five (71%) of the mutation-positive FNA samples had a malignant diagnosis after surgery. Moreover, there was only an 8% cancer risk in nodules with an indeterminate cytological diagnosis but with a negative molecular test.

CONCLUSION

This study demonstrates that thyroid FNA can be analysed successfully by NGS. The detection of mutations known to be involved in thyroid cancer improves the sensitivity of thyroid FNA diagnosis.