What is a Thyroid?

The thyroid is a butterfly-shaped gland located in the front part of the neck, below the Adam’s apple. In most people it cannot be seen or felt. The thyroid gland takes iodine (a mineral found in iodized salt and some foods) from the diet and blood and uses it to make several of the hormones that it produces and stores. Some of those hormones help regulate heart rate, body temperature, blood pressure and the rate that food is converted into energy.

It consists of two lobes, the right and the left, and is joined by a narrow isthmus. The lobes resemble the wings of a butterfly and the isthmus represents the body. The thyroid is normally larger in women during menstruation and pregnancy.

Thyroid Cancer

Thyroid cancer accounts for approximately 1% of all cancers, with around 12,000 Americans being diagnosed each year.

The thyroid gland contains two main types of cells: C cells, which make a hormone known as calcitonin, and the thyroid follicle cells, which make a thyroid protein called thyroglobulin and do the actually creating and storing of the thyroid hormone.

Cancer develops differently in each cell. Cancer is formed when the body’s cells begin to reproduce in a rapid and haphazard manner, causing an abundance of some and a shortage of others. The excess creates a mass of tissue known as a tumor.

A bump in the neck (thyroid nodule) is often the first sign of a thyroid tumor because the thyroid gland is so close to the skin. They can appear at any age but are found more often in adults.

Most tumors (over 90%) found in the thyroid gland tend to be benign (non-cancerous). Benign thyroid nodules develop from the follicular cells and can be found in both enlarged and normal-sized glands, in multiple numbers or singular. If the gland has more than one nodule, it is called a multinodular goiter.

Malignant Thyroid Tumors

Just 5%-10% of thyroid nodules turn out to be malignant. Malignant (cancerous) tumors are able to spread into nearby tissues and can travel via the bloodstream to other parts of the body and create tumors at those sites. This long distance travel and colonization is called metastasizing.

There are four major types of thyroid cancer: papillary, follicular, medullary, and anplastic. The doctors are able to differentiate between them by the way that they look under the microscope and their growth patterns.

Papillary Tumors

Papillary cancer, also known as papillary carcinoma or papillary adenocarcinoma, are usually very slow-growing and develop from the thyroid follicle cells. The cancerous cells appear as tiny mushroom-shaped patterns in the tumor.

Papillary tumors sometimes involve both lobes, but are most often found in only one lobe. There are several different subtypes of this carcinoma (cancer). Despite its slow growth, it can quickly spread into the lymph nodes (bean sized collections of infection-fighting white cells) of the neck. Even so, the prognosis for this most common form of thyroid cancer is usually good.

Follicular Thyroid Cancer

This is the second most common type of thyroid cancer. It is also known as follicular carcinoma or follicular adenocarcinoma. These tumors are surrounded by a thin layer of tissue called a capsule and are more common in countries with widespread iodine deficiencies in their diets. This form of thyroid cancer tends to stay in the gland but do sometimes spread to areas such as the lungs and bones.

The follicular cancer spreads to the lymph nodes less than the papillary type, but the prognosis tends to be the about the same or slightly worse.

Anaplastic Thyroid Cancer

Anaplastic tumors are rare sorts that usually appear in people over 60 years of age and are believed to develop from a primary (existing first) follicular or papillary cancer. They are the fastest growing of the thyroid tumors and quickly invade the neck area and metastasize to other sites and causing a high number of fatalities. In contrast to the others, when viewed beneath the microscope, anaplastic cancer cells have very little resemblance to normal thyroid tissue and are therefore referred to as undifferentiated.

Medullary Thyroid Cancer (MTC)

This is the only form of thyroid cancer to develop in the non-hormone producing C cells. These tumors often produce carcinoembryonic antigen (CEA), which a hormone produced by some cancers that can be found by taking a blood test. Although these tumors are slow-growing in terms of invading the nearby tissues and organs, they metastasize quickly and are often found to have traveled to the lung, liver or lymph nodes by the time of the initial diagnosis.

There are two different types of MTC. One is called isolated familial medullary cancer (FTMC) and inherited through the family genetics. The other one, sporadic MTC, makes up most of the MTC cases, occurs in only one lobe, and is not hereditary.

Symptoms

The most common sign of thyroid cancer is the nodule appearing in the neck. Some health care professionals suggest checking your neck at least twice a year for abnormal growths.

Sometimes there is pain in the thyroid area of the neck, or traveling up the neck to the ear area. That may be accompanied by difficulty breathing or swallowing, swollen lymph nodes, hoarseness, or a cough unaccompanied by a cold.

Any of those symptoms could also be associated with other non-cancerous health conditions, but a trip to the doctor should be scheduled for a professional assessment of the situation.

Diagnosing Thyroid Cancer

There are several imaging tests that may be performed to learn the size and location of a nodule, including:

Radioactive iodine scan (thyroid scan) – the use of radioactive iodine and a special machine to outline the abnormal areas of the thyroid.

Ultrasonography (ultrasound) – the use of high-frequency sound waves to create images of the thyroid.

Computed tomography (CT or CAT scan) – an x-ray procedure with a machine that rotates around your body taking multiple pictures.

Magnetic resonance imaging (MRI or MRI scan) – use of strong magnets, radio waves, and a computer instead of x-rays to take images of the thyroid.

Octreotide scan – done with a radioactively tagged hormone to evaluate the metastasis of medullary cases.

To determine if a nodule is benign or malignant, the cells must be observed beneath a microscope. A sample will be taken either by withdrawing tissue with a needle (needle biopsy) or removing the whole tumor (surgical biopsy.)

Once the diagnosis is complete, the doctors move on to the staging process.

Staging

The staging process involves determining the extent of the cancer for treatment and prognosis (likely outcome) purposes. The most common system used for thyroid cancer staging is the TNM system of the American Joint Committee on Cancer (AJCC; in conjunction with an international cancer committee).

T = Tumor size

N = Node involvement

M = Metastasis situation

Those letters are combined with other numbers and letters to indicate severity and combinations. The system looks like this:

The classifications for T:

TX: Primary tumor cannot be assessed (information unavailable)

T0: No evidence of primary tumor

T1: The tumor is 2 cm or smaller

T2: Tumor is between 2 cm and 4 cm

T3: Tumor is larger than 4 cm or has slightly grown outside the thyroid

T4a: Tumor of any size and has grown beyond the thyroid gland to invade nearby tissues

T4b: Tumor has grown into the spine or into nearby large blood vessels

The classifications for N:

NX: Regional (nearby) lymph nodes cannot be assessed

N0: No regional lymph node spread

N1: Spread to lymph nodes

N1a: Spread to lymph nodes in the neck (cervical lymph nodes)

N1b: Spread to lymph nodes in the upper chest (upper mediastinal lymph nodes)

The classifications for M:

MX: Presence of distant metastasis (spread) cannot be assessed

M0: No distant metastasis

M1: Distant metastasis is present, involving nonregional lymph nodes, internal organs, bones, etc.

Stage grouping consists of combining several TNM descriptions into more distinct stages. While most other cancers are stage-grouped, thyroid cancer is different in that it is grouped into categories that take in to account the type of cancer and the patient’s age. Other cancers tend to be generalized. (The following chart portion is taken from the American Cancer Society at www.cancer.org)

Stage Grouping for Papillary or Follicular Thyroid Carcinoma

All staging systems have found that older people have a greater chance of dying from papillary or follicular thyroid cancer. The TNM stage groupings for papillary and follicular carcinomas take this fact into account and places all people under age 45 years with papillary thyroid cancer in stage I if they have no distant spread and stage II if they have distant metastases beyond the neck or upper mediastinal lymph nodes.

Patients younger than 45 years

Stage I: Any T, any N, M0: The cancer can be any size and may or may not have spread to lymph nodes. It has not spread to distant sites.

Stage II: Any T, any N, M1: The cancer can be any size and may or may not have spread to lymph nodes. It has spread to distant sites.

Patients 45 years and older

Stage I: T1, N0, M0: The cancer is less than 2 cm and has not spread to lymph nodes or distant sites.

Stage II: T2, N0, M0: The cancer is 2 to 4 cm and has not spread to lymph nodes or distant sites.

Stage III: T1-3, N0-N1a, M0: The cancer is larger than 4 cm or has grown slightly outside the thyroid and has not spread to lymph nodes or distant sites; or it is any size and has spread to local neck nodes but not to distant sites.

Stage IVA: T1-4a, N0-1b, M0: Tumor of any size and has grown beyond the thyroid gland to invade nearby tissues of the neck and may or may not have spread to local lymph nodes but not to distant sites; or it is any size and has spread to lymph nodes in the upper chest (upper mediastinal lymph nodes) but not to distant sites.

Stage IVB: T4b, Any N, M0: Tumor has grown either back to the spine or into nearby large blood vessels, may or may not have spread to lymph nodes, but has not spread to distant sites.

Stage IVC: Any T, any N, M1: Tumor is any size and may or may not have spread to lymph nodes, but it has spread to distant sites.

Stage Grouping for Medullary Thyroid Carcinoma

Stage grouping for medullary thyroid carcinoma is the same as for papillary or follicular carcinoma in people older than age 45.

Stage Grouping for Anaplastic/Undifferentiated Thyroid Carcinoma

All anaplastic thyroid cancers are considered as stage IV, reflecting the poor prognosis of this type of cancer.

Stage IVA: T4a, any N, M0: Tumor of any size and has grown beyond the thyroid gland to invade nearby tissues of the neck and may or may not have spread to local neck nodes but not to distant sites.

Stage IVB: T4b, Any N, M0: Tumor of any size has grown either back to the spine or into nearby large blood vessels, may or may not have spread to lymph nodes, but has not spread to distant sites.

Stage IVC: Any T, any N, M1: Tumor is any size and may or may not have spread to lymph nodes, but it has spread to distant sites.

Thyroid Carcinoma Stage Grouping

Papillary or Follicular Under 45 Years

Stage I Any T Any N M0

Stage II Any T Any N M1

Papillary or Follicular 45 Years and Older

Stage I T1 N0 M0

Stage IIT2 N0 M0

Stage III T3 N0 M0, T1 N1a M0, T2 N1a M0, or T3 N1a M0

Stage IVA T4a N0 M0, T4a N1a M0, T1 N1b M0, T2 N1b M0, T3 N1b M0, or T4a N1b M0

Stage IVB T4b Any N M0

Stage IVC Any T Any N M1

Medullary Carcinoma

Stage I T1 N0 M0

Stage II T2 N0 M0

Stage III T3 N0 M0, T1 N1a M0, T2 N1a M0, T3 N1a M0

Stage IVA T4a N0 M0, T4a N1a M0, T1 N1b M0, T2 N1b M0, T3 N1b M0, T4a N1b M0

Stage IVB T4b Any N M0

Stage IVC Any T Any N M1

Anaplastic Carcinoma All anaplastic carcinomas are considered Stage IV

Stage IVA T4a Any N M0

Stage IVB T4b Any N M0

Stage IVC Any T Any N M1

Treatments

The treatment plan the doctor chooses will include one or more of the following:

Surgery: This is the most common treatment; either part or the entire thyroid is removed, along with lymph nodes or any other affected tissue.

External Radiation Therapy: High energy rays are delivered from a machine and directed to the tumor in order to kill cancer cells or slow the rate of their reproduction.

Chemotherapy: A family of systematic (circulates through the entire body through the bloodstream) anti-cancer drugs that can be taken through the mouth, into the vein, or in shot form.

Thyroid Hormone Therapy: Hormone replacement pills taken to compensate for the body’s inability to produce the thyroid hormone after surgery.

Radioactive Iodine Therapy: Radioactive iodine can destroy the thyroid gland without affecting anywhere else.

Survival Rates

Relative 5-year survival rates (as of the 2003 American Cancer Society statistics) for papillary thyroid cancer are as follows:

Stage I – 100%

Stage II – 100%

Stage III – 96%

Stage IV – 45%

For follicular thyroid cancer:

Stage I – 100%

Stage II – 100%

Stage III – 79%

Stage IV – 47%

For medullary thyroid cancer:

Stage I – 100%

Stage II – 97%

Stage III – 78 %

Stage IV – 24%

Compared to many other cancers, those are pretty good survival rates. And considering that it's estimated that one in three people will be diagnosed with cancer in their lifetime, thyroid cancer patients almost seem fortunate. I think I would prefer those odds to the ones I get with Acute Lymphblastic Leukemia, but hey, I'm still breathing so I'm not complaining...