Thyroid nodules are a very common condition, and you may have a relative, friend or colleague with a thyroid nodule. As medical checkups become more routine and the resolution of screening instruments such as ultrasound improves, more and more people are found to have thyroid nodules each year. The incidence of thyroid nodules increases with age, being 10 to 100 times more common in adults than in children, and four times more common in women than in men. Thyroid nodules are divided into three main categories, namely benign, cancerous and cystic. Benign nodules are subdivided into cystic nodules, solid nodules, follicular adenomas, and congenital developmental abnormalities; cancerous nodules are divided into four types, namely papillary thyroid cancer, follicular thyroid cancer, medullary thyroid cancer, and undifferentiated thyroid cancer; and cystic nodules are divided into simple, degenerative, cancerous, parathyroid cysts, and inflammatory.