Thyroid nodules are very common, and their frequency is four to five times higher in women than in men. Most of them are benign, with only a very little percentage revealing a malignant neoplasm. About 50% of thyroid nodules are detected by self-palpation of neck, whereas the other 50% are diagnosed by neck ultrasonography and following fine-needle aspiration. Management of thyroid nodules is very difficult, because benign nodules are prevalent, whereas thyroid carcinoma is uncommon, representing only 1% of all malignancies. A standard diagnostic approach is represented by 'first-level' exams, consisting in neck ultrasonography and serum thyroid-stimulating hormone measurement, followed, only for nodules that are suspicious of malignancy, by 'second-level' exams, consisting of fine-needle aspiration and mutational test, which does detect particular DNA mutations present only in malignant cells. In this review, we will analyze the genetics of thyroid cancer and its heterogeneity, and we will briefly describe the current available diagnostic and therapeutic approaches.