Thyroid Cancer (Gudmundsson, 2017) – Is Thyroid Cancer Genetic?

Nebula Genomics DNA Report for Thyroid Cancer

Is thyroid cancer genetic? We created a DNA report based on a study that attempted to answer this question. Below you can see a SAMPLE DNA report. To get your personalized DNA report, purchase our Whole Genome Sequencing!

Is thyroid cancer genetic? Sample report from Nebula Genomics
Is thyroid cancer genetic? Sample report variants from Nebula Genomics

Introduction (Part 1 of Is thyroid cancer genetic?)

The thyroid is a butterfly-shaped gland located at the base of your neck. It produces hormones that regulate your heart rate, blood pressure, body temperature, amount of calcium in the blood, metabolism. Although it may not produce any symptoms at the early stage, it can grow and result in pain and swelling in the neck area. As tumors grow, signs of the disease include:

  • A lump (nodule) that can be felt through the skin on your neck mass 
  • Changes to your voice, including increasing hoarseness
  • Difficulty swallowing
  • Pain in your neck (especially the front of the neck) and throat
  • Swollen lymph nodes in your neck

What is thyroid cancer? This cancer is generally slow growing and highly treatable. In aggressive forms, it may spread to lymph nodes, causing further complications. The thyroid cancer ribbon is made of three colors: purple, teal, and pink.

Epidemiology (Part 2 of Is thyroid cancer genetic?)

According to the American Thyroid Association, ATA, this type of cancer is rare relative to other cancer types. In recent decades, incidence has risen worldwide. There are significant differences depending on region and ethnicity. Some of this increase can be contributed to improved testing techniques. 

This cancer is the eighth most common cancerous disease in the United States, accounting for 4% of all new cases. According to the National Cancer Institute, the rate of new cases of thyroid cancer was 15.7 per 100,000 men and women per year. The death rate was 0.5 per 100,000 men and women per year and Approximately 1.3 percent of men and women will be diagnosed with it at some point during their lifetime, based on 2015–2017 data.

Types (Part 3 of Is thyroid cancer genetic?)

Thyroid cancer is the most common tumor of the endocrine system. It is divided into different types, of which the most common type often occurs in young adulthood. The age peak is on average 52 years for women and 55 years for men. Disturbing thyroid nodules are usually the first symptom. The most common types of thyroid cancer include:

  1. Papillary: (75 to 85% of cases, normally occurs between ages of 35 and 60). These carcinomas originate from the thyroid cells and form finger-like branched (papillary) structures. They are the most frequent malignant neoplasms of this disease. They metastasize (spread to distant parts of the body) mainly via the lymph vessels (lymphogenic metastasis) into the lymph nodes of the neck. The risk of developing papillary thyroid cancer, papillary type, is increased in women with familial adenomatous polyposis and in patients with Gardner syndrome. These syndromes are caused by defects in the gene APC.
  2. Follicular: (10 to 20% of cases, normally occurs between ages of 40 and 50) – this form of thyroid cancer is occasionally seen in people with Cowden syndrome. Some include Hürthle cell carcinoma as a variant and others list it as a separate type.In this carcinoma, the tissue structure largely resembles the structure of a mature or developing thyroid gland. The diseased cells originate from the thyroid cells and form metastases (distant metastasis) in the lungs, skeleton and brain, and blood vessels, mainly via the bloodstream
  3. Medullary: (5 to 8% of cases, normally occurs between ages of 40 and 50) – cancer of the parafollicular c cells, calcitonin-producing cells (also called C-cells), which are located in the thyroid gland due to developmental connections, but are not related to the actual thyroid function
  4. Anaplastic: (less than 5% of cases, normally occurs around 60 years of age) is not responsive to treatment and can cause pressure symptoms. Chemotherapy may be recommended as a treatment of anaplastic thyroid cancer at the time of diagnosis. 
  5. Poorly differentiated thyroid cancer is a malignant neoplasm of follicular cell origin showing intermediate histopathological patterns between differentiated and undifferentiated thyroid cancers
A tissue sample of papillary thyroid cancer
Papillary thyroid carcinoma. Nephron. Attribution-Share Alike 3.0 Unported

Is Thyroid Cancer Genetic?

The causes are not fully understood in detail although a combination of environmental and genetic factors are each thought to play some role, especially for the hereditary forms. 

Familial medullary thyroid carcinoma (FMTC), occurring in about 2 out of 10 medullary thyroid carcinomas (MTCs), results from inheriting an abnormal gene. 

According to the American Cancer Society, the combination of FMTC and tumors of other endocrine glands is called multiple endocrine neoplasia type 2 (MEN 2). There are 2 subtypes, MEN 2a and MEN 2b, caused by genetic mutations in the RET gene.

“In MEN 2a, MTC occurs along with pheochromocytomas (tumors that make adrenaline) and with parathyroid gland tumors.

In MEN 2b, MTC is associated with pheochromocytomas and with benign growths of nerve tissue on the tongue and elsewhere called neuromas. This subtype is much less common, but also more aggressive, than MEN 2a.”

In these inherited forms of MTC, the cancers often develop during childhood or early adulthood and can spread early. Having a first-degree family member (parent, brother, sister, or child) with the disease, even without a known inherited syndrome in the family, increases your risk of thyroid cancer. 

The papillary type often runs in families. Genes on chromosome 19 and chromosome 1 are suspected of causing these familial cancers.

Persons who have Carney complex, type I or Cowden disease are at increased risk for developing both papillary and follicular thyroid cancers. The former syndrome is caused by defects in the gene PRKAR1A and the latter is most often caused by defects in the gene PTEN. 

Non-genetic Causes (Part 5 of Is thyroid cancer genetic?)

This disease occurs more often in women than in men. 

There is also a causal connection with iodine deficiency (about 2.3 times higher risk). Radiation (especially in childhood and adolescence) also plays a significant role. After the atomic bombs were dropped on Hiroshima and Nagasaki, the risk of this cancer increased many times over in the affected areas. The same applies to the areas affected by massive radioactive fallout after the Chernobyl disaster. People living in the United States during the atomic bomb tests between the 1940s – 1960s may also be exposed. The radioactive substance, Iodine 131 (or I-131) released from these atomic explosions collects in the thyroid gland, which causes the increased risk. You can reduce your risk by avoiding areas with high levels of radioactivity. 

Symptoms (Part 6 of Is thyroid cancer genetic?)

Typically, a nodule formation in the area of the thyroid gland is noticed. This gland may be enlarged or remain normal in size. Enlarged neck lymph nodes can also appear before a palpable thyroid node. Dysphagia, hoarseness as an expression of vocal cord nerve paralysis, a lack of thyroid gland ability to shift the swallowing action, rough consistency, and fused lymph nodes are late symptoms of advanced disease.

Diagnosis (Part 7 of Is thyroid cancer genetic?)

A medical provider will physically examine the neck area to check for indications of an enlarged thyroid. They will also inquire about risk factors such as radiation exposure and personal or family history of the disease. Minimally invasive tests such as blood tests, ultrasound imaging tests on the neck, PET scans, and CT scans may help the doctor determine whether the organ is functioning properly and if suspicious nodules are present. A fine needle aspiration (thin needle) biopsy of the thyroid tissue may be acquired to determine if cancerous cells are present. If diagnosed with medullary type, the doctor may recommend a genetic test and/or genetic counseling to look for genes that may increase your risk for other cancers. To learn more about clinical DNA tests, take a look at our blog. You may be particularly interested in:

  • Ambry Genetics – risks of various disease types
  • Color – risks of cancer, genetic forms of heart disease, and medication responses
  • Invitae – diagnostics, proactive health, and reproductive health
  • Myriad Genetics – diagnostics, reproductive tests, and precision medicine tests
  • Veritas Genetics – disease risks and carrier screenings

Some very small tumors that have a low risk of spreading in the body might not need treatment right away. Instead, you might consider active surveillance with frequent monitoring of the cancer. Monitoring might require blood tests and a thyroid cancer ultrasound exam of your neck once or twice per year.

Diagram showing stage T3 thyroid cancer.
Diagram showing stage T3 thyroid cancer. Cancer Research UK / Wikimedia Commons. 

Treatment (Part 8 of Is thyroid cancer genetic?)

To treat thyroid cancer, treatment options include thyroid cancer surgery to remove all or part of the thyroid, radioiodine therapy, and radiation therapy. 

Surgical removal

In most cases, the gland must be completely removed (total thyroidectomy). If the disease is not aggressive, medical providers may choose to save some of the thyroid (thyroid lobectomy), especially if the patient is under 45 years old. The majority of these cancers are diagnosed before they have metastasized, or disease that has spread outside of the thyroid. 

An exception is the so-called microcarcinoma. In this case, only the affected lobe is surgically removed and no subsequent radioiodine therapy is performed.

In addition to the removal of the gland, occasionally the lymph nodes around that area are also removed (lymphadenectomy), since the lymph nodes may be affected by the cancer. However, at least in the case of papillary and follicular cancers, this is only recommended if there is clinical evidence or suspicion of regional lymph node metastasis. In medullary thyroid carcinoma, the corresponding guidelines recommend unilateral or even bilateral cervical lymphadenectomy. 

Following the operation, the gland function is replaced by thyroid hormone replacement therapy called levothyroxine. This medication supplies the missing hormone the organ would normally produce, and it suppresses the production of thyroid-stimulating hormone (TSH) from your pituitary gland, which could stimulate any remaining thyroid cancer cells to grow.

Diagram showing after surgery for medullary thyroid cancer
Diagram showing after surgery for medullary thyroid cancer with the central lymph nodes and the thyroid gland removed. Cancer Research UK / Wikimedia Commons.  Attribution-Share Alike 4.0 International.

Radioactive iodine therapy

After surgery, iodine-storing carcinomas are followed by radioactive iodine treatment to remove the postoperative remaining thyroid tissue (ablation) in cases of papillary or follicular carcinoma. Radioactive iodine-131 is administered, which accumulates exclusively in the gland tissue. Some side effects of this therapy include:

  • Metallic taste in your mouth
  • Dry mouth
  • Sore throat
  • Neck pain
  • Nausea or vomiting, which is usually mild
  • Constipation or diarrhea
  • Fatigue
  • Unusually low (hypothyroidism) or unusually high (hyperthyroidism) thyroid levels

Treatment of advanced carcinoma

Advanced carcinoma is defined as a thyroid carcinoma with distant metastases (e.g. lung metastases) or a non-operable carcinoma. In this case, a complete cure is usually no longer possible. The aim of the therapy is to prolong life with the highest possible quality of life and to reduce thyroid tumor-related symptoms.

Several tyrosine kinase inhibitors (TKI), a type of targeted therapy, have been approved for metastatic differentiated cancer that no longer responds to radioiodine therapy, including sorafenib and lenvatinib. Cabozantinib and vandetanib are approved for advanced medullary cancer. Clinical trials for other drugs are ongoing.

Radiation therapy

External radiation therapy may be advised if surgery isn’t an option and the cancer grows after radioiodine therapy. Radiation therapy may also be recommended after surgery if there’s an increased risk that your cancer will recur.

Recurrence (Part 9 of Is thyroid cancer genetic?)

This disease may come back, even after surgery and treatment. This could happen if diseased cells spread to other areas of the body before the gland is removed. Reoccurrence may happen in:

  • Lymph nodes in the neck
  • Small pieces of thyroid tissue left behind during surgery
  • Other parts of the body, such as the lungs and bones

It is important to monitor signs and symptoms with a medical provider long term.

Prognosis and Survival Statistics (Part 10 of Is thyroid cancer genetic?)

Differentiated carcinomas

In most cases, average 10-year thyroid cancer survival rates are more than 90% for these thyroid cancer patients undergoing management of papillary thyroid carcinoma and approximately 80% for the follicular variant (on treatment). According to the National Cancer Institute, the overall 5-year survival rate for patients with thyroid cancer is 98%. Prognosis factors include patient age as well as tumor type and stage, tumor size, spread and histological differentiation; lymph node metastases do not appear to significantly affect the prognosis. Due to the increased risk of recurrence, consistent follow-up is extremely important.

Medullary and anaplastic thyroid carcinoma

The following 5-year survival rates for patients with anaplastic thyroid cancer and medually cancer apply on average (at treatment):

  • Medullary carcinoma: 60-70%
  • Anaplastic carcinoma: about 5 % 

Did you know you can test for thyroid hormone levels at home? Learn more in our article about at home thyroid tests.

You can also see our posts in the Genetic Cancer Testing series and explore the Nebula Research Library to learn about hundreds of other conditions influenced by genetics, including many cancers.

December 1, 2020