Definition

Thyroid cancer starts in cells in a gland in the neck. Cancer cells grow out of control and form a tumor. It can also invade and damage nearby tissue.

Thyroid Cancer Copyright © Nucleus Medical Media, Inc.

There are several types of thyroid cancer:

• Papillary carcinoma (most common type)—It usually grows very slowly but often spreads to lymph nodes.
• Follicular carcinoma (second most common type)—It usually stays in the thyroid gland, but can spread to other parts of the body. Common areas of spread include the lungs and bones. It does not usually spread to the lymph nodes. This type of thyroid cancer is often curable when found early.
• Anaplastic carcinoma (rare form of thyroid cancer)—Quickly invades the neck and other parts of the body. This form is often fatal.
• Medullary thyroid carcinoma (MTC)—Often spreads to the lymph nodes, lungs, or liver before a thyroid mass has been found. There are 2 types of MTC:
  • Sporadic MTC
  • Familial medullary thyroid carcinoma (FMTC)
• Thyroid lymphoma (rare type of thyroid cancer)

Causes

Cancer occurs when cells grow and develop without control or order. It is not clear exactly what causes these cells to develop. A combination of genetics and environment probably play a role.

Risk Factors

Thyroid cancer is more common in women. Though it can happen at any age it is more common in people aged 30 years and older. Other factors that may increase your chances of thyroid cancer include:

• Diet low in iodine
• History of radiation to the head, neck, or chest, especially in infancy or childhood
• Family history of thyroid cancer
• Obesity
• Acromegaly—excess growth hormone
• Sjogren syndrome
• Exposure to radioactive fallout from nuclear accidents or exposed to nuclear testing area during childhood

Symptoms

Thyroid cancer may cause:

• A lump in the neck, usually over the thyroid
• Neck pain (sometimes going up to the ears)
• Hoarseness
• Difficulty swallowing
• Difficulty breathing
• Persistent cough
• Enlarged lymph glands in the neck

Diagnosis

A bump in thyroid may be felt during an exam. It may also be seen during a test for something else. The doctor will ask about your symptoms and medical history. A physical exam will also be done. This may include a careful exam of your neck. To look for changes in the thyroid the doctor may order:

• Blood tests—to look for hormone changes
• Thyroid scan
• Ultrasound

A fine needle aspiration may be done. It will remove a small sample of tissue for biopsy. The tissue will show if cancer cells are there.

The care team will use all test results to determine the type and stage of cancer. Staging is used to guide your treatment plan. Like other cancers, thyroid cancer is staged from 1 to 4. Cancer that has stayed on one area is called Stage 1. The higher the stage the further the cancer has spread. Cancer that has spread to other parts of the body is called stage 4.

Early detection and treatment lead to better outcomes. Your doctor may recommend screening tests if you are at high risk for thyroid cancer. For example:

• Have a thyroid exam every 3 years if you are aged 20-39 years.
• Have a thyroid exam every year if you are aged 40 years or older.

Treatment

The goal of treatment is to remove as much of the cancer as possible. Most thyroid cancers can be cured. Those that can't be cured may need to be managed to delay or prevent the spread of cancer. Specific treatment step depend on the stage and type of cancer. Options may include:

• Thyroidectomy—Removal of all or part of the thyroid gland. Cancer can spread to lymph nodes on the neck. The nodes may need to be removed for testing or treatment.
• Radioactive iodine therapy—shrinks and destroys cancer and thyroid tissue. Iodine is naturally absorbed by the thyroid. This helps to focus the treatment to the thyroid without affecting the rest of the body.
• External radiation therapy—A radiation beam is directed at the tumor from outside the body. It will kill cancer cells and shrink tumors. May only be helpful in certain types of thyroid cancer.

Chemotherapy is not often used. However, it may be used to treat cancer that has spread in the body.

Thyroid treatment and removal will affect the amount of hormones. Medicine may be needed to take place of missing or lower hormones.

Prevention

Exposure to radiation is a major risk factor for thyroid cancer. The thyroid should be checked often if there has been radiation to head, neck, or chest.