Thyroid FNA diagnostics study

“A 9-gene molecular signature enhances diagnosis of thyroid nodular goiter”

Tsoumalis G., Kalimani E., Sarantopoulou C., Moraitis D., and Nikolopoulos SN.

Center for Molecular Analysis and Research SA, Agrinio, Greece

Background
Although FNA is currently considered to be the best initial diagnostic test for evaluation of a thyroid
nodule, it cannot always discriminate between benign and malignant thyroid tumors. To address this
issue, we developed a molecular assay for thyroid FNAs that tests both the expression of genes that
becoming expressed in cancerous thyroid tissues, as well as the presence of the oncogenic BRAF V600E
mutation.

Methodology
We used a cohort of 102 cases (105 nodules), 88 women and 14 men, aged 46,6 +/- 15 years old,
presented with nodular or multinodular, non toxic goiter. Thyroid ultrasound guided FNABs were
performed. Tissue from 2 aspirations of the needle were used for a cytological examination. A third
aspiration was transferred into a tube containing nucleic acids stabilization buffer. A molecular 9-gene
signature that tests the expression of 8 genes encoding cell surface receptors and oncogenes and the
presence of BRAF V600E mutation was performed, by quantitative real-time PCR.

Results
A positive 9-gene signature was obtained in 20 cases (19%). Agreement between gene signature and
cytology assessment was found in 102 out of 105 nodules (97%). Three cases (15.7% of all positive
cases) were positive for malignancy by gene signature and negative by cytological criteria. However, all 3
cases were found to be positive for malignancy after surgery, which underscores the value of this
molecular assessment. We have validated this gene signature with surgical samples from 29
thyroidectomies. BRAF V600E mutation was absent only in one case of a positive biopsy.

Conclusion
We developed a combined gene expression and mutation analysis assay as an accurate tool for
determining the presence/absence of malignancy in thyroid FNAs. This methodology will enhance the
diagnosis of thyroid nodules, particularly in those cases in which it is necessary to resolve uncertainties.

Oral presentation,

Presented at American Thyroid Association Conference, Quebec, Canada, September 21 2012