Thyroid nodules and evaluation of thyroid cancer risk

General aspects Palpable thyroid nodules occur in about 6% of women and 2% of men with higher prevalence in the elderly and in iodine-deficient areas. However, the great majority of thyroid nodules are impalpable and asymptomatic with an estimated prevalence of 20–76% in the general population. These small nodules are increasingly detected by neck ultrasound and parallel the rising incidence of small differentiated thyroid cancer over the last two decades. The most common causes of thyroid nodules are colloid nodules, Hashimoto’s and subacute thyroiditis, cysts, follicular adenomas and thyroid cancer. The presenting clinical problems include hyperthyroidism, pain (often due to haemorrhage into a cyst) and compressive symptoms (due to a multinodular goitre). However, the clinical priority in the initial management of a thyroid nodule is to evaluate its thyroid cancer risk to guide decision regarding thyroidectomy. Thyroid cancer occurs in 5–15% of nodules. Approximately 90% of all thyroid cancers are differentiated thyroid cancer, 85% of which are papillary cancer. The evaluation of thyroid cancer risk considers the clinical picture, thyroid function, ultrasound characteristics of the nodule and, depending on the ultrasound appearance, fine-needle aspiration biopsy (FNAB).