Thyroid nodules are very common in the general population. They are detected in about five percent of individuals during a physical examination. Half the population's thyroid nodules are found by ultrasound or other imaging studies of the thyroid gland. About 93-95 percent of these nodules are benign and five to seven percent are malignant. There are many different types of benign (non-cancerous) thyroid nodules which are listed below:
- Colloid nodule: The most common type of benign nodule, consisting of enlarged growths of normal thyroid tissue. Even if colloid nodules should grow, they remain localized to the thyroid.
- Follicular adenoma: Another type of benign nodule.
- Thyroid cyst: Areas of the thyroid that contain fluid and sometimes a combination of fluids and solids (complex cysts). They can range from less than 1/3 inch in diameter to more than one inch. If a cyst is filled with fluid, it is benign. If they cyst has a combination of fluids and solids, it can be malignant.
- Inflammatory nodule: Caused by thyroiditis, it is a chronic inflammation of the thyroid gland. These nodules are generally painless. A rare type of thyroiditis, called subacute thyroiditis, can cause pain in the thyroid gland.
- Multinodular goiter: An enlargement of thyroid gland is a goiter. Enlargement can be caused by thyroid nodules, which is known as a multinodular goiter. This can cause tightness in the throat, voice changes, as well as difficulty breathing or swallowing.
- Hyperfunctioning thyroid nodule (toxic adenoma, toxic multinodular goiter, Plummer's disease): These nodules can produce their own thyroid hormones, irrespective of the TSH made by the pituitary gland (which regulates the thyroid). Hyperfunctioning thyroid nodules produce high levels of thyroxine which results in low levels of TSH. Another cause of an overactive thyroid gland is a genetic defect of TSH receptors in the thyroid gland.
Most thyroid malignancies are called well-differentiated thyroid cancer. Well-differentiated thyroid cancer includes papillary carcinoma of the thyroid (which accounts for 80 to 90 percent of thyroid cancers) and follicular carcinoma of the thyroid (which accounts for approximately 10 to15 percentof thyroid cancers). Another three to five percent of thyroid cancers are medullary carcinoma of the thyroid and a very small percentage are anaplastic carcinomas. For more information on these types of thyroid cancer, please visit: