Thyroid Cancer in Brief

Thyroid cancer is the growth of malignant cells in the thyroid, a gland comprising two large lobes flanking the windpipe (trachea) at the base of the neck. There are four basic types of thyroid cancer: papillary, follicular, medullary and anaplastic.

Papillary carcinomaaccounts for over 80 percent of thyroid cancers. Such tumors tend to grow very slowly and often take years to spread to other sites.
Follicular carcinoma, the second most common type, is also slow growing, but like papillary carcinoma, it can spread to the lungs and to bone tissue. Medullary carcinomas are much rarer; they are aggressive but highly curable if detected and treated while still confined exclusively to the thyroid. Anaplastic carcinomais more common in the elderly and highly malignant; death usually occurs within six months of diagnosis. Fortunately, it is the least common form of thyroid cancer.

Most cases of thyroid cancer occur between the ages of 25 and 65, and women are more commonly affected than men. The prognosis depends heavily upon the type of malignancy involved and the age of the patient; the outlook is generally quite good, and the mortality rate is low.

Causes

The cause of thyroid cancer is unknown, but previous radiation therapy to the thyroid area (for acne, enlarged thymus gland, tonsils or adenoids) is a significant risk factor, especially if it was administered during infancy or early childhood. Malignancies may appear as soon as five years or as late as 30 years after radiation.

Exposure to radioactive fallout is associated with an increased incidence of thyroid cancer. Medullary carcinoma frequently occurs as a genetic disorder in members of the same family. Familial medullary carcinoma is often associated with a type of adrenal tumor and overgrowth of the parathyroid glands. Papillary and follicular carcinoma, the two most common types, also appear to be linked to hereditary factors.

Symptoms

• A firm or hard, usually painless lump in the front of the neck
• Swelling in the neck (goiter)
• Swallowing difficulty
• Hoarseness or changes in the voice
• Cough, possibly bloody
• Breathing difficulty
• Unexplained bone fractures (occurs with follicular carcinoma)
• Severe flushing or diarrhea (occurs with medullary carcinoma)

Prevention

Avoid X-rays to the neck or upper chest areas as much as possible. Frequent screening for elevated calcitonin levels is recommended in family members of patients with medullary cancer.

Diagnosis

Patient history should include any childhood radiation treatments, as well as any family history of thyroid cancer. Physical examination of the nodule to identify whether it is solitary or part of a cluster, common in benign goiters. A fine-needle biopsy (use of a small-gauge needle and syringe to take a tissue sample for examination under a microscope) may identify malignant cells.

When medullary carcinoma is suspected, blood levels of calcitonin, a thyroid hormone, are measured. (High calcitonin levels may indicate medullary carcinoma.) Genetic testing is now available to determine susceptibility in family members of patients with medullary carcinoma.

Radioiodine thyroid scanning may be used to determine if the nodule is "cold," or nonfunctioning; 10 percent of cold nodules are malignant. Ultrasound may determine the consistency of the tumor or mass. Suppressive doses of thyroid hormone may be given to see whether the nodule shrinks or disappears, indicating a benign tumor.

Treatment

Near-total surgical removal of the thyroid (thyroidectomy) is done in almost all cases. Removal of surrounding lymph nodes and other tissues may also be warranted. Radioactive iodine therapy may be used to destroy thyroid tissue left behind after thyroidectomy or to treat thyroid cancer that has spread to the lungs or the bones.

The absence of thyroid tissue after thyroidectomy requires lifetime supplementation with thyroid hormone (thyroxine), which also reduces the risk of cancer recurrence.

Treatment for rare anaplastic carcinoma consists primarily of supportive therapy to make the patient as comfortable as possible.

When to call your doctor

Call a doctor as soon as you detect an unusual lump in your neck, especially if it rapidly increases in size. Although thyroid cancer is rare, all such growths should be examined.

Last Updated: 1/15/2003
The Johns Hopkins University 1996-2003.  All rights reserved.  This information is not intended to provide advice on personal medical matters, nor is it intended to be a substitute for consultation.