Thyroid nodules may be single or multiple. A thyroid gland that contains multiple nodules is referred to as a multinodular goiter. If the nodule is filled with fluid or blood, it is called a thyroid cyst. If the nodule produces thyroid hormone in an uncontrolled manner without regard to the body's needs, the nodule is referred to as autonomous. This type of nodule may cause signs and symptoms of too much thyroid hormone or hyperthyroidism. Occasionally, patients with a thyroid nodule may have too little thyroid hormone or hypothyroidism. This is most often seen when the hypothyroidism is caused by Hashimoto's thyroiditis, an inflammatory, autoimmune disease of the thyroid gland.
The most common types of noncancerous, single thyroid nodules are colloid nodules or follicular adenomas. Another type of benign nodule that may be seen is called a Hurthle cell adenoma. Only a minority of nodules are cancerous.
Cancerous nodules are classified by the types of malignant thyroid cells they contain. These cell types include papillary, follicular, medullary, or poorly differentiated (anaplastic) cells. The prognosis for the patient depends largely on the cell type and how far the cancer has spread by the time it is discovered.
In addition to thyroid cancer of the cell types mentioned, thyroid nodules may contain lymphoma, a cancer of the immune system. Cancer from other sites, such as breast and kidney, also can spread (metastasize) to the thyroid gland.
The cause of most thyroid nodules is not known. In certain cases, a lack of iodine in the diet can cause the thyroid gland to develop nodules. There also are certain genes that may be involved in the development of nodules in some individuals.
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Archived: March 20, 2014
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