[Molecular diagnostics of thyroid nodule]

Nodular goiter is a very frequent occurrence that rarely requires surgical treatments. Only a few of these nodules are the site of carcinoma which requires surgery. It is therefore necessary to precisely determine the nature of the nodule. The cytological examination of the biopsy performed with a fine needle is the most accurate diagnostic method for determining the benign or malignant nature of a thyroid nodule. However, in approximately 15% of cases the cytology is indeterminate. In these cases, it is possible to apply the knowledge of molecular biology to refine the diagnosis. Mutations of the BRAF and RAS genes and recombinations of the RET, TRK and PAX8/PPARγ genes are the most frequent genetic alterations in thyroid carcinomas. However, except for BRAF mutation, these genetic alterations are not pathognomonic of carcinoma. The new tests that combine the gene expression profile and the search for specific genetic alterations have excellent reliability in excluding the malignant nature of a nodule with indeterminate cytology, but they still have an unsatisfactory specificity, and their cost limits their use.