Molecular fine-needle aspiration biopsy diagnosis of thyroid nodules by tumor specific mutations and gene expression patterns

Fine-needle aspiration biopsy (FNAB) is currently the most sensitive and specific tool for the presurgical differential diagnosis of thyroid malignancy, but has also substantial limitations. While approximately 75% of FNAB reveal benign lesions and 5% already cytologically prove malignancy, up to 20% of FNAB show follicular proliferation for which follicular adenoma, follicular carcinoma, and follicular variant of papillary carcinoma can only be distinguished histologically, thus requiring thyroid surgery. However, new biomarkers that might improve the accuracy of FNAB come along with the discovery of more and more details of the molecular etiology of thyroid tumors. So far molecular testing for somatic mutations is most promising (e.g., BRAF), since the proposed biomarkers from mRNA- and miRNA-expression studies need further evaluation, especially in FNAB samples. Nevertheless, the application of molecular markers will significantly improve thyroid tumor diagnosis and thus it will help to prevent unnecessary surgeries and it will also help to guide mutation-specific targeted therapies.