Overview

Definition

The thyroid gland is a small, butterfly-shaped organ in the center of the neck just below the Adam's apple. The thyroid produces hormones that maintain metabolism, body heat as well as the rate at which your body uses nutrients from food. The thyroid also produces calcitonin, which regulates the amount of calcium in your blood. Thyroid cancer usually arises from hormone-producing cells, which have become malignant and is the most common endocrine cancer.

The patient first notices thyroid cancer as a distinct lump or focus of gland enlargement. Often, there are no other symptoms. On the other hand, goiter -- the diffuse enlargement of the thyroid gland -- causes symptoms of hyperthyroidism (bulging eyes, rapid heart-rate), but is not cancer. Although nodules may occur within a goiter, they are usually not indicative of thyroid cancer.

Nodules may be fluid-filled or solid lumps that move up and down with the Adam's apple. About five percent of thyroid nodules are malignant, and do not cause symptoms. About half of adults in the United States will develop a benign thyroid nodule at some time during their lives. However, there are only about 30,180 new cases of thyroid cancer diagnosed each year. Most cases of thyroid cancer are completely cured, with a nearly 90 percent survival rate five years after diagnosis.

Types of thyroid cancer

Papillary thyroid cancer is the most common type of thyroid cancer (accounting for 70 percent to 80 percent of thyroid cancers) and can occur at any age.

Follicular thyroid cancer (accounting for 10 percent to 15 percent of thyroid cancers) tends to spread faster and is usually discovered at an advanced stage.

Medullary thyroid cancer (accounting for 3 percent to 5 percent of thyroid cancers) is occasionally part of a familial syndrome associated with multiple endocrine tumors, called multiple endocrine neoplasia type 2 (MEN2) and may be diagnosed by genetic testing. Most medullary thyroid cancers, however, are sporadic. Tumor cells arise from thyroid parafollicular cells or "C-cells," which produce calcitonin -- a hormone involved in calcium regulation. The calcitonin level rises when MTC returns, making it a good marker for recurrence.

Anaplastic thyroid cancer (accounting for less than 5 percent of thyroid cancers) occurs mostly in older patients and is the least likely to respond to treatment.

More on Thyroid Cancer

In the Encyclopedia:

This article was reviewed and updated June 2007.