New insights into the diagnosis of nodular goiter

Preoperative diagnostic investigations of nodular goiter are based on two main examinations: ultrasonography of the thyroid gland and ultrasound-guided fine-needle aspiration biopsy. So far, FNAB has been the best method for the differentiation of nodules, but in some cases it fails to produce a conclusive diagnosis. Some of the biopsies do not provide enough material to establish the diagnosis, in some other biopsies cytological picture is inconclusive. Determining the eligibility of thyroid focal lesions for surgery has been more and more often done with molecular methods. The most common genetic changes leading to the development of thyroid cancer include mutations, translocations and amplifications of genes, disturbances in gene methylation and dysregulation of microRNA. The mutations of Ras proto-oncogenes and BRAF gene as well as disturbances of DNA methylation in promoter regions of genes regulating cell cycle (e.g. hypermethylation of RASSF1A gene and TIMP-3 gene) play an important role in the process of neoplastic transformation of thyreocyte. The advances in molecular biology made it possible to investigate these genetic disturbances in DNA and/or RNA from peripheral blood, postoperative thyroid tissue material and cytology specimens obtained through fine-needle aspiration biopsy of focal lesions in the thyroid gland. As it became possible to analyze the mutations and methylation of genes from cell material obtained through fine-needle aspiration biopsy, it would be beneficial to introduce the techniques of molecular biology in the pre-operative diagnosis of nodular goiter as a valuable method, complementary to ultrasonography and FNAB. The knowledge obtained from molecular studies might help to determine the frequency of follow-up investigations in patients with nodular goiter and to select patients potentially at risk of developing thyroid cancer, which would facilitate their qualification for earlier strumectomy.