The thyroid is a small, butterfly-shaped gland situated at the base of the neck, just below Adam's apple. 
The thyroid is a small, butterfly-shaped gland situated at the base of the neck, just below Adam's apple. 

The thyroid is a small, butterfly-shaped gland situated at the base of the neck, just below Adam's apple. Thyroid cancer is the abnormal growth and uninhibited multiplication of cells of the thyroid gland. This ultimately results in loss of nutrients for the healthy body cells and eventual cell death. The thyroid gland is part of the endocrine system, which regulates hormones in the body.

The thyroid gland absorbs iodine from the bloodstream to produce thyroid hormones, which regulate a person’s metabolic rate. A tumor can be cancerous or benign. A tumor is considered cancerous when it has the potential to grow and spread to other parts of the body.

How is thyroid cancer diagnosed?

Thyroid cancer is diagnosed in the following ways:

  • Physical assessment: The doctor obtains a detailed medical history and performs a physical assessment. A healthy thyroid gland is barely palpable. If a tumor develops in the thyroid, it is felt as a lump in the neck.
  • Blood tests: A thyroid blood test checks the thyroid hormone levels and gauges whether the thyroid gland is functioning properly. In most cases of thyroid cancer, the thyroid hormone levels (T3, T4 and thyroid stimulating hormone or TSH) are normal. Tumor markers are special proteins that could be elevated in certain kinds of thyroid cancer. These should be checked as well. The marker for the medullary type of carcinoma of the thyroid is calcitonin and carcinoembryonic antigen (CEA) protein.
  • Biopsy: During a fine-needle aspiration biopsy, the health care provider removes cells from the thyroid nodule to test for cancer cells. A sentinel node biopsy can determine if cancer cells have spread to the nearest lymph nodes. The health care provider may use ultrasound technology to guide these biopsy procedures. Biopsy gives an accurate diagnosis and can also determine the type of thyroid cancer.
  • Radioiodine scan: This test can detect thyroid cancer and determine if cancer has spread. The patient is asked to swallow a pill containing a safe amount of radioactive iodine (radioiodine). Over a few hours, the thyroid gland absorbs the iodine. Then, the health care provider uses a special device to measure the amount of radiation in the gland. Areas with less radioactivity (cold spots) need to be tested to confirm the presence of cancer.
  • Imaging scans: Magnetic resonance imaging (MRI), computed tomography (CT) and positron emission tomography (PET) scans can detect thyroid cancer and cancer spread.

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Types of cells in the thyroid gland

Thyroid cancer starts when healthy cells in the thyroid change and grow out of control, forming a mass called a tumor. The thyroid gland contains two types of cells:

  1. Follicular cells: These cells are responsible for the production of thyroid hormone. The thyroid hormone is vital for living because the hormone controls the basic metabolism of the body. It controls how quickly the body burns calories. This can affect weight loss and weight gain, slow down or speed up the heartbeat, raise or lower body temperature, influence how quickly food moves through the digestive tract, control the way muscles contract and control how quickly dying cells are replaced.
  2. C cells: These special cells of the thyroid make calcitonin, which is a hormone that participates in calcium metabolism.

Types of thyroid cancers

Different types of thyroid cancer include

  • Papillary thyroid cancer: This is the most common form of thyroid cancer. It arises from the cells in the thyroid gland that produce and store thyroid hormones (follicular cells). Papillary thyroid cancer occurs most commonly in people 30 to 50 years of age, but it can occur at any age.
  • Follicular thyroid cancer: Follicular thyroid cancer also arises from the follicular cells of the thyroid. It commonly presents in those older than 50 years of age. Hurthle cell cancer is rare and more aggressive variant of follicular thyroid cancer. Papillary thyroid cancer and follicular thyroid cancer together are sometimes referred to as differentiated thyroid cancer.
  • Anaplastic thyroid cancer: Anaplastic thyroid cancer is a rare type of thyroid cancer that usually occurs in older patients older than 60 years of age. It is extremely aggressive and grows rapidly. It is difficult to treat and has a poor response to treatment.
  • Medullary thyroid cancer: Medullary thyroid cancer arises in the C cells in the thyroid gland. C cells produce a hormone called calcitonin. Elevated levels of calcitonin in the blood may indicate medullary thyroid cancer at an early stage. Calcitonin levels also help to monitor the effectiveness of treatment.
  • Other rare types: Though extremely rare, some types of cancer can arise in the thyroid, such as thyroid lymphoma (arises from the immune cells of the thyroid) or thyroid sarcoma (arises from the connective tissue cells in the thyroid).

What are the signs and symptoms of thyroid cancer?

It is common for people with thyroid cancer to have a few vague or no symptoms initially. Thyroid cancers are often diagnosed by routine examination of the neck during a general physical exam. People with thyroid cancer may experience the following sign and symptoms:

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Medically Reviewed on 5/4/2021
References
Sharma PK. Thyroid Cancer. Medscape. https://emedicine.medscape.com/article/851968-overview

American Thyroid Association. Thyroid Cancer (Papillary and Follicular). https://www.thyroid.org/thyroid-cancer/