The great advance of molecular medicine over the last few years gives us an attractive vision of the new possibilities in diagnosis and therapeutics of thyroid cancer and helps us to understand its biological behaviour. The clinical application of the growing understanding of gene alterations involved in thyroidal oncogenesis is becoming a reality. Such knowledge might contribute to greater diagnostic accuracy, by helping us characterise malignant or benign cells, predict tumour outcome or state its origin. Likewise it might be useful to know the response to conventional therapies or the future implications of pharmacogenetics. In addition molecular medicine applications ought to be considered in determining the prognosis of spontaneous and familiar carcinomas. Such information can significantly improve current clinical-pathologic prognostic methods