Review of the genetics of thyroid tumours: diagnostic and prognostic implications

Background: Thyroid nodules are common, but only a small proportion harbour malignancy. Despite this, the frequency of thyroid cancer is on the increase and thyroid malignancy is the most common endocrine malignancy. Preoperative diagnosis is based on ultrasound and radionucleotide imaging as well as the fine-needle aspiration biopsy (FNAB). These biopsies yield a large proportion of indeterminate results due to inadequate material for cytological diagnosis, or due to the cytological similarity of FAs and follicular carcinomas. Recent advances in the understanding of the molecular pathogenesis of thyroid malignancy have led to the detection of characteristic genetic alterations in FNABs. This technology has the potential to increase the specificity of this test, combining cytological with genetic testing to reduce the number of indeterminate results, thereby reducing the number of thyroidectomies performed for benign disease. Methods: This review examines the evidence for the presence of the common genetic alterations in thyroid cancer and outlines the pathological and clinical correlations of these mutations. The practicality and utility of measuring these genetic alterations in FNAB specimens is also outlined as well as the potential for these tests to alter primary management and follow-up of patients with nodular thyroid disease. Conclusion: It is likely that a combination of molecular testing and cytological examination of FNAB specimens will prove to be the most efficient and specific method of diagnosing thyroid cancer preoperatively.