Thyroid Cancer

Introduction

Anatomy

Causes

The exact cause of most thyroid cancers is unknown.  Cancer occurs when cells grow abnormally and out of control, instead of dividing in an orderly manner.  Thyroid cancer is more common in women than in men.  It occurs most frequently between the ages of 20 and 60 years old.

Some cases of thyroid cancer may be linked to changes in DNA.  Your DNA is the carrier of your genetic information, including directions for how your cells divide.  You inherited your DNA from your parents.  People with a family history of thyroid cancer have an increased risk for developing thyroid cancer.

Exposure to radioactivity from nuclear reactive material, nuclear plant accidents, or some types of radiation therapy for cancer can increase the risk for thyroid cancer.  In some parts of the world, diets that are low in iodine increase the risk for thyroid cancer.  This is not a concern in the United States, since iodine is contained in table salt and many of the foods we eat.

There are several types of thyroid cancer.  Some of the more common types of thyroid cancer include:

Papillary carcinoma

The majority of thyroid cancers are papillary carcinomas.  They occur most frequently in women of childbearing age.  Papillary carcinoma originates in the thyroid follicle cells.  It is generally a very slow growing cancer that may gradually spread to other parts of the body.  Papillary carcinoma tends to spread to the lymph nodes in the neck, most of the time this is very treatable.  Papillary cancer is the least likely type of thyroid cancer to cause death.

Follicular carcinoma
Follicular carcinoma is the second most common type of thyroid cancer.  It is more common in countries where people do not eat enough iodine in their diets.  This is not a common situation in the United States where people ingest iodine in table salt and food on a regular basis.  Follicular carcinoma usually remains in the thyroid gland, but it may spread to the lungs and bone.  Follicular carcinoma tends to return.  Cancer that comes back after treatment is termed recurrent

Medullary carcinoma of the thyroid (MCT)
MCT develops in the C cells of the thyroid gland.  MCT can quickly spread to the lymph nodes, liver, and lungs.  Most cases of MCT are sporadic.  However, isolated familial medullary thyroid carcinoma (FMTC) is a type of thyroid cancer that is inherited and can occur in each generation of a family.  MCT does not respond to radioactive iodine treatments and tends to have a poor prognosis.

Anaplastic carcinoma
Anaplastic carcinoma is also called undifferentiated thyroid cancer, giant cell cancer, and spindle cell cancer.  It is rare.  Anaplastic carcinoma is an aggressive cancer.  It can spread very quickly to nearby throat and neck structures.  Anaplastic carcinoma does not respond to radioactive iodine treatments.  It is the most deadly form of thyroid cancer.

Symptoms

Diagnosis

Treatment

Prevention

Am I at Risk

Most people that develop thyroid cancer have no apparent risk factors.  However, researchers have identified risk factors that may increase the likelihood of developing thyroid cancer.  People with all of the risk factors may never develop the condition; however, the chance of developing thyroid cancer increases with the more risk factors you have.  You should tell your doctor about your risk factors and discuss your concerns.

Risk factors for thyroid cancer:

_____ Thyroid cancer is three times more common in women than in men.
_____ Most cases of thyroid cancer occur in people between the ages of 20 and 60.
_____ Follicular thyroid cancer is more common in people with a low-iodine diet. Papillary thyroid cancer is more common in people with a low-iodine diet that have been exposed to radioactivity.  In the United States, people consume iodine in salt and foods so this is not as great of a risk factor as it may be for people living in other parts of the world.
_____ During the 1950s, radiation treatments were used to treat acne, fungus infections of the scalp, and enlarged glands or tonsils. Adults that received head and neck radiation treatments in childhood have an increased risk for developing papillary thyroid cancer.
_____ Children that receive low dose radiation treatments for non-Hodgkin’s lymphoma have an increased risk of developing thyroid cancer.
_____ People that have been exposed to radioactive fallout from nuclear reactive material, nuclear weapons testing, or power plant accidents have an increased risk for developing thyroid cancer. 
_____ An inherited abnormal gene causes some medullary thyroid cancers.  If familial medullary thyroid carcinoma (FMTC) runs in your family, ask your doctor to get tested.
_____ Gardner syndrome, familial polyposis, and Cowden disease are inherited genetic conditions that are associated with higher rates of thyroid cancer.
_____ Certain families appear to have an excess number of papillary thyroid cancers.  Researchers have not identified the genetic link as of yet.  However, you should let your doctor know if your relatives have thyroid cancer.

Complications

Advancements