This information is provided by SSCHRC to help you understand thyroid cancer and its management. It is written in a patient-friendly and medically accurate style.
Thyroid cancer originates in the thyroid gland, a small, butterfly-shaped gland situated in the front of the neck, near the base of the throat. It is typically a slow-growing disease that generally responds well to treatment.
The thyroid gland comprises two halves, or lobes, positioned on either side of the windpipe (trachea) just beneath the voice box (larynx, or Adam's apple). A narrow band of tissue, known as the isthmus, connects these two lobes.
As an integral part of the body's endocrine system, the thyroid is responsible for producing hormones that regulate vital bodily functions, including heart rate, blood pressure, body temperature, and metabolism (the process of converting food into energy). While its function is crucial, thyroid cancer rarely affects the gland's ability to produce hormones, and there is no established link between thyroid cancer and common thyroid conditions such as hyperthyroidism.
This is the most common category, further divided into well-differentiated and poorly differentiated. Well-differentiated cancer cells closely resemble normal, healthy cells. Patients with well-differentiated thyroid cancers have the highest probability of being disease-free following treatment.
The types include:
This aggressive form represents just 1% of all thyroid cancer cases. Sometimes called undifferentiated thyroid cancer, it is the rarest and most dangerous type. These tumours often begin as papillary, follicular, or Hürthle cell cancers and develop aggressive mutations. Anaplastic thyroid cancer grows and spreads very rapidly, and its growth can impact the windpipe, leading to breathing difficulties. Immediate treatment is essential. SSCHRC's Anaplastic Thyroid Cancer Clinic provides the immediate, specialised treatments these patients require.
MTC is unique as it is the only type that develops from the parafollicular cells (C cells) of the thyroid gland, which produce calcitonin to help control calcium metabolism. MTC accounts for less than 5% of thyroid cancers. MTC is most successfully treated when diagnosed before it has spread.
There are two main types of MTC:
A risk factor increases a person's likelihood of developing a specific disease. Less than 1% of thyroid cancers are linked to risk factors other than age and gender. Known risk factors include:
Exposure to high levels of radiation, especially during childhood: This is the most significant risk factor, typically from radiation treatment to the head and neck area for a childhood cancer. Routine medical procedures like dental X-rays involve very low levels of radiation and are not considered risk factors.
Familial medullary thyroid cancer is usually caused by an inherited mutation in the RET gene, making individuals who inherit the gene highly likely to develop the cancer. A family history of thyroid cancer, parathyroid disease, or adrenal tumours warrants discussion with a doctor about genetic counselling to manage risk.
The thyroid needs iodine to produce hormones. Low iodine levels can increase the risk of thyroid cancer. This is uncommon in regions where iodine is added to table salt.
Over half of all thyroid cancer cases occur between the ages of 20 and 55. Women are three times more likely than men to develop the disease, with papillary thyroid cancer being found most often in women of childbearing age.
Important Note: It is important to note that having risk factors does not guarantee a thyroid cancer diagnosis. Any concerns about risk factors should be discussed with your doctor.
Thyroid cancer often presents with few or no signs in its early stages. When symptoms do appear, they may vary but can include:
Important Note: Most patients experiencing these symptoms do not have thyroid cancer, but any persistent signs should be evaluated by a medical professional as they may indicate other health issues.
Achieving an accurate diagnosis is the crucial first step toward successful thyroid cancer treatment. At SSCHRC's Endocrine Centre, our experts are highly experienced and skilled in diagnosing, staging, and treating thyroid cancer.
Thyroid cancer is often found incidentally during routine medical imaging. If an image reveals a growth (nodule) on the thyroid, your doctor will conduct a thorough examination, including questions about your symptoms, general health, and family medical history.
These allow doctors to visualise cancerous growths inside the body. Ultrasound is the most common initial exam for diagnosis. Advanced techniques like CT and PET scans may be used later, typically for aggressive forms of thyroid cancer, to determine the extent of the disease.
This is the definitive way to diagnose thyroid cancer. A small tissue sample is removed and examined under a microscope for cancer cells. A biopsy is usually ordered when an initial imaging scan shows a thyroid nodule. Thyroid biopsies are performed by a radiologist who uses ultrasound to guide a needle into the nodule. Only about 12% of biopsied thyroid nodules are found to be cancerous; the rest are benign (non-cancerous).
This scan may be used after thyroid surgery for well-differentiated thyroid cancer. The patient takes a liquid form of radioactive iodine. Since well-differentiated thyroid cells absorb iodine, a scanner can then identify any remaining cancer cells or spread to other parts of the body. This test is ineffective for medullary or anaplastic thyroid cancer, as those cells do not absorb iodine.
Hormone levels related to thyroid function are typically tested when cancer is suspected. This helps determine the nature of the suspected growth and the health of the gland. However, thyroid cancer usually does not impair the thyroid's function, and most people with thyroid cancer have a normally functioning thyroid.
Patients with medullary thyroid cancer should have a blood test to check for the genetic mutation that causes the hereditary form of the disease. A positive result means the patient's first-degree relatives should also be tested, as over 90% of those with the mutation will eventually develop the hereditary form of MTC. Genetic testing of the tumour and blood can also help identify treatment options, including clinical trials, for aggressive thyroid cancers.
Effective treatment requires care from doctors with a high level of expertise. SSCHRC has one of the largest thyroid cancer treatment programmes in the country, ensuring physicians are among the most skilled and experienced.
If diagnosed, your doctor will discuss the best treatment plan, which is determined by:
Surgery is the most common and effective treatment for most types of thyroid cancer. For some small and localised cancers, especially when diagnosed early, active surveillance (monitoring) or ablation may be considered. Outcomes are best when the procedure is performed by an experienced thyroid surgeon.
The extent of surgery may include:
Thyroid cancer is the only cancer treated with radioactive iodine. RAI is effective for most well-differentiated thyroid cancer cells (papillary and follicular types) because they naturally absorb iodine. It is not effective for anaplastic or medullary thyroid cancer, as those cells do not absorb iodine.
After a thyroidectomy, RAI is used to:
Targeted therapy drugs are designed to interfere with specific molecules (often proteins) on a cellular level that cancer cells require to survive, multiply, and spread. They are especially useful for advanced or metastatic thyroid cancer that no longer responds to RAI, and for aggressive types such as medullary or anaplastic thyroid cancer. Targeted therapy is usually an oral daily pill and requires close monitoring for side effects.
The immune system's ability to eliminate cancer is improved with immunotherapy. Immune checkpoint inhibitors are a type of immunotherapy that stops the immune system from prematurely shutting down the attack on cancer. Patients may receive a single drug or a combination of drugs via intravenous (IV) infusion. Treatment sessions typically last 30 minutes to a few hours and are given once every two to six weeks.
Chemotherapy drugs work to kill cancer cells, control their growth, or alleviate disease-related symptoms. It is rarely used to treat thyroid cancer because most types do not respond well to traditional drugs. However, it may be considered for aggressive and fast-growing anaplastic thyroid cancer, or if the cancer has spread extensively and is no longer responding to surgery, RAI, or targeted therapy.
Radiation therapy uses focused beams of energy to destroy cancer cells, accurately targeting the tumour while minimising damage to healthy tissue. External beam radiation therapy is generally reserved for the most aggressive thyroid cancers and is important in treating anaplastic thyroid cancer, medullary thyroid cancer, cancers that do not absorb iodine, and recurrences in the neck or other hard-to-reach areas.
Following surgery, many patients require thyroid hormone replacement therapy, which not only maintains normal body function but also helps prevent cancer recurrence. For patients with well-differentiated thyroid cancer, hormone treatment may be used to reduce the level of thyroid-stimulating hormone (TSH), as high levels of this hormone could promote the growth of thyroid cancer cells. Regular blood tests are necessary to monitor TSH levels and ensure the correct medication dosage.
Most people with thyroid cancer, especially those with well-differentiated types, lead long, healthy lives. However, ongoing care is vital for monitoring recurrence and managing life without a thyroid.