Thyroid nodules are lumps which commonly arise within an otherwise normal thyroid gland. They are often located at the edge of the thyroid gland so they can be felt or even seen as a lump in the throat. Usually benign tissue growths, or cysts which are filled with fluid, occasionally thyroid nodules can take on characteristics of malignancy and require surgical excision.
Thyroid nodules are common in the general population but are four to six times more common in females: one in 12 to 15 women has a thyroid nodule; one in 40 to 50 men has a thyroid nodule. About half of the thyroid nodules detected on physical examination are solitary nodules; as many as 50% of a population will have a nodule somewhere in their thyroid. In one study, 4% of cases of solitary nodules were due to Hashimoto's thyroiditis.
The frequency of thyroid nodules increases with age. Most nodules are detected between the ages of 30 and 50 years and the majority of them (over 90%) are benign (non-cancerous growths). The importance of solitary thyroid nodule lies in the increased risk of malignancy compared with other thyroid swellings. The incidence of malignancy in solitary thyroid nodules varies from 5% to 20% in different surveys, whereas the incidence of malignancy in multinodular goitre is only 3-5%.