What are the types of thyroid cancer?
Thyroid cancer has a variety of warning signs including the appearance of a lump in the front of the neck.
Thyroid cancer arises from the cells of the thyroid gland. The thyroid is a butterfly-shaped gland located in the front of the neck, just below Adam's apple. The thyroid gland produces hormones (chemicals) that regulate body weight, temperature, blood pressure and heart rate.
Thyroid cancer is classified on the basis of the type of cells present in the tumor. The treatment and prognosis depend on the type of thyroid cancer.
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 between the ages of 30 and 50, 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 over the age of 50. Hurthle cell cancer is a rare variant of follicular thyroid cancer and is more aggressive. Papillary thyroid cancer and follicular thyroid cancer are sometimes referred together as differentiated thyroid cancer.
- Anaplastic thyroid cancer: Anaplastic thyroid cancer is a rare type of thyroid cancer that usually occurs in older patients over the age of 60. It is very aggressive and grows rapidly. It is very difficult to treat with a poor prognosis. Anaplastic thyroid cancer typically occurs in adults who are 60 years of age and older.
- 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 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).
How is thyroid cancer treated?
The treatment may involve one or a combination of multiple treatment modalities, which depend on the extent and type of cancer.
The treatment options include
- Surgery: It may involve removing all (total thyroidectomy) or most of the thyroid (near-total thyroidectomy). Removal of lymph nodes in the neck (lymph node dissection) may or may not be performed.
- Thyroid hormone therapy: After thyroidectomy surgery, thyroid hormone medication needs to be taken for a lifetime to replace thyroid hormone levels.
- Radioactive iodine: Radioactive iodine treatment uses large doses of radioactive iodine and is usually used after surgery. It destroys the remaining thyroid tissue and microscopic thyroid cancer. Most of the radioactive iodine is excreted in the urine a few days after treatment.
- External radiation therapy: This targets and selectively kills cancer cells and shrinks tumors using radiation.
- Chemotherapy: Chemotherapy is a drug treatment given intravenously (IV) that uses chemicals to kill cancer cells.
- Targeted drug therapy: Targeted drug treatments focus on specific abnormal proteins in cancer cells. The drugs block the abnormalities and can cause death of the cancer cells.
- Injecting alcohol into cancers: Alcohol ablation involves injecting small thyroid cancers with alcohol using radiological guidance which causes the thyroid cancer to shrink.
- Palliative (supportive) care: This is specialized medical care that focuses on providing relief from pain and other serious symptoms.
What causes thyroid cancer?
The exact cause of thyroid cancer is not known, but various factors increase the risk of thyroid cancer. The common risk factors include
- Genetic predisposition and certain genetic syndromes, such as familial medullary thyroid cancer, multiple endocrine neoplasia, familial adenomatous polyposis and Cowden's syndrome
- History of breast cancer
- Female sex
- Radiation exposure because of cancer treatment, occupation or its presence in the environment
- Age: Thyroid cancer is more common in those who are over the age of 40.
What are the warning signs of thyroid cancer?
The common signs and symptoms of thyroid cancer include
- A swelling in the anterior part of the neck which is painless initially
- Difficulty swallowing
- Difficulty breathing due to compression of the trachea (windpipe)
- Change in voice
- Cough
- Weight loss
- Palpitations
How is thyroid cancer diagnosed?
The physician performs a complete clinical assessment. Complete blood analysis and radiological tests are performed (ultrasound, computed tomography [CT], magnetic resonance imaging [MRI] and radioactive iodide imaging). Genetic testing may be done if genetic syndromes are suspected. A biopsy can help confirm the diagnosis and identify the type of thyroid cancer. Biopsy is a minimally-invasive procedure that involves obtaining a small sample of thyroid tissue with the help of a needle and then studying it under the microscope.