Thyroid Cancer: Types and Treatment
Thyroid cancer is a disease in which malignant (cancer) cells form in the tissues of the thyroid gland. The thyroid gland is a small, butterfly-shaped gland located at the base of the neck, just below the Adam’s apple. It produces hormones that regulate metabolism, heart rate, blood pressure, and body temperature. While thyroid cancer is relatively uncommon compared to other cancers, it is the most common endocrine cancer. This article provides a comprehensive overview of thyroid cancer, including its types, causes, symptoms, diagnosis, treatment options, and prognosis.
Early detection and treatment are crucial for the best possible outcome.
Thyroid Cancer
Types of Thyroid Cancer
There are several different types of thyroid cancer, classified by the type of cell from which they originate. The most common types are differentiated thyroid cancers, which arise from follicular cells.
Types of Thyroid Cancer
- Papillary Thyroid Cancer: The most common type, accounting for about 80% of all thyroid cancers. It tends to grow slowly and often spreads to lymph nodes in the neck. It has a very good prognosis, especially in younger patients.
- Follicular Thyroid Cancer: The second most common type, accounting for about 10-15% of all thyroid cancers. It’s more likely to spread to distant organs, such as the lungs and bones, than papillary thyroid cancer. The prognosis is generally good, but slightly less favorable than papillary cancer.
- Hürthle Cell Cancer: A subtype of follicular thyroid cancer that is often more aggressive.
- Medullary Thyroid Cancer (MTC): Arises from the parafollicular cells (C cells) of the thyroid gland, which produce calcitonin, a hormone that helps regulate calcium levels in the blood. MTC can be sporadic (not inherited) or familial (inherited). It accounts for about 4% of thyroid cancers.
- Anaplastic Thyroid Cancer: A rare and aggressive form of thyroid cancer that grows and spreads very quickly. It accounts for about 1-2% of all thyroid cancers and has a poor prognosis.
- Poorly Differentiated Thyroid Cancer: An intermediate grade between differentiated and anaplastic thyroid cancers.
- Thyroid Lymphoma: A rare type of cancer that starts in the immune cells of the thyroid gland.
Causes and Risk Factors for Thyroid Cancer
The exact cause of most thyroid cancers is unknown, but several risk factors have been identified.
Risk Factors
- Radiation Exposure: Exposure to ionizing radiation, especially in childhood, is a significant risk factor for thyroid cancer. This includes radiation from medical treatments (e.g., radiation therapy for head and neck cancers) and nuclear fallout.
- Family History: Having a family history of thyroid cancer, especially medullary thyroid cancer, increases the risk.
- Certain Genetic Conditions:
- Multiple Endocrine Neoplasia type 2 (MEN2): A genetic syndrome that increases the risk of medullary thyroid cancer and other endocrine tumors.
- Familial Medullary Thyroid Carcinoma (FMTC): An inherited form of medullary thyroid cancer.
- Cowden Syndrome: A genetic disorder that increases the risk of various cancers, including thyroid cancer.
- Familial Adenomatous Polyposis (FAP): A genetic condition that increases the risk of colon cancer and, to a lesser extent, thyroid cancer.
- Age: Thyroid cancer can occur at any age, but it’s most common in people over 30, and the risk increases with age. Anaplastic thyroid cancer is most common in people over 60.
- Sex: Women are about three times more likely to develop thyroid cancer than men.
- Iodine Deficiency or Excess: Both iodine deficiency and excessive iodine intake may increase the risk of certain types of thyroid cancer.
- Being of Asian descent.
Symptoms of Thyroid Cancer
Many people with thyroid cancer have no symptoms, especially in the early stages. The most common symptom is a lump or nodule in the neck.
Common Symptoms
- A Lump or Nodule in the Neck: This is the most common symptom and may be painless.
- Swelling in the Neck:
- Hoarseness or Voice Changes: If the cancer affects the nerves that control the vocal cords.
- Difficulty Swallowing (Dysphagia):
- Difficulty Breathing: If the cancer is large enough to press on the trachea (windpipe).
- Cough: A persistent cough that is not related to a cold or other respiratory illness.
- Pain in the Neck or Throat:
- Swollen Lymph Nodes in the Neck:
Note: Most thyroid nodules are *not* cancerous. However, any lump or swelling in the neck should be evaluated by a doctor.
Diagnosing Thyroid Cancer
Diagnosing thyroid cancer involves a combination of physical examination, imaging tests, and a biopsy.
Diagnostic Tests
- Medical History and Physical Examination: The doctor will ask about your symptoms, medical history, family history, and risk factors. They will also examine your neck, feeling for any lumps or swelling in the thyroid gland and lymph nodes.
- Thyroid Ultrasound: This is the most important imaging test for evaluating thyroid nodules. Ultrasound uses sound waves to create images of the thyroid gland and can help determine the size, shape, and characteristics of any nodules. It can also help identify suspicious features that may suggest cancer.
- Fine-Needle Aspiration (FNA) Biopsy: This is the most accurate way to determine if a thyroid nodule is cancerous. A thin needle is inserted into the nodule, and cells are withdrawn for examination under a microscope.
- Blood Tests:
- Thyroid Function Tests (TSH, T4, T3): These tests are usually normal in people with thyroid cancer, but they can help rule out other thyroid conditions.
- Calcitonin: Measured to help diagnose and monitor medullary thyroid cancer.
- Carcinoembryonic Antigen (CEA): Also measured to help diagnose and monitor medullary thyroid cancer.
- Thyroglobulin: Measured after thyroidectomy for differentiated thyroid cancers to monitor for recurrence.
- Radioactive Iodine Scan: May be used after surgery for differentiated thyroid cancers to detect any remaining thyroid tissue or cancer cells.
- CT Scan, MRI, or PET Scan: These imaging tests may be used to determine the extent of the cancer or to look for spread to other parts of the body.
- Genetic Testing: May be recommended for people with medullary thyroid cancer or a family history of thyroid cancer to identify genetic mutations that increase the risk of the disease.
Treatment for Thyroid Cancer
Treatment for thyroid cancer depends on the type and stage of the cancer, as well as the individual’s overall health.
Treatment Options
- Surgery (Thyroidectomy): The most common treatment for thyroid cancer. The entire thyroid gland (total thyroidectomy) or a part of it (lobectomy) may be removed. Lymph nodes in the neck may also be removed if the cancer has spread.
- Radioactive Iodine (RAI) Therapy: Used after surgery for differentiated thyroid cancers (papillary and follicular) to destroy any remaining thyroid tissue or cancer cells. Radioactive iodine is taken orally and is absorbed by thyroid cells.
- Thyroid Hormone Replacement Therapy: After thyroidectomy or RAI therapy, lifelong thyroid hormone replacement therapy with levothyroxine is needed to replace the hormones normally produced by the thyroid gland.
- External Beam Radiation Therapy (EBRT): Uses high-energy X-rays to kill cancer cells. May be used to treat anaplastic thyroid cancer or other types of thyroid cancer that have spread.
- Chemotherapy: Rarely used for thyroid cancer, but may be used to treat anaplastic thyroid cancer or other types of thyroid cancer that have spread and are not responding to other treatments.
- Targeted Therapy: Drugs that target specific molecules involved in cancer cell growth. Used to treat advanced differentiated thyroid cancers that are no longer responding to RAI therapy, and for medullary thyroid cancer. Examples include sorafenib, lenvatinib, vandetanib, and cabozantinib.
- Clinical Trials: Participation in clinical trials may be an option for some people with thyroid cancer.
Prognosis for Thyroid Cancer
The prognosis for thyroid cancer is generally very good, especially for differentiated thyroid cancers (papillary and follicular). The 5-year survival rate for localized papillary and follicular thyroid cancer is nearly 100%. Even for advanced stages, survival rates are relatively high compared to many other cancers.
Medullary thyroid cancer has a less favorable prognosis than differentiated thyroid cancers, but it is still often treatable. Anaplastic thyroid cancer has a very poor prognosis.
Factors that affect prognosis include:
- Type of thyroid cancer
- Stage of the cancer (size of the tumor and whether it has spread)
- Age at diagnosis
- Overall health
- Response to treatment
FAQ – Frequently Asked Questions About Thyroid Cancer
Q1. Can thyroid cancer be prevented?
A1. There’s no guaranteed way to prevent thyroid cancer, but you can reduce your risk by avoiding exposure to radiation, especially in childhood. If you have a family history of thyroid cancer or certain genetic conditions, talk to your doctor about genetic testing and screening.
Q2. Is thyroid cancer curable?
A2. Many thyroid cancers, especially papillary and follicular thyroid cancers, are highly treatable and often curable with surgery and/or radioactive iodine therapy.
Q3. What are the long-term side effects of thyroid cancer treatment?
A3. The most common long-term side effect of thyroid cancer treatment is hypothyroidism (underactive thyroid), which requires lifelong thyroid hormone replacement therapy. Other potential side effects depend on the specific treatment and may include:
- Surgery: Scarring, hypoparathyroidism (low calcium levels), vocal cord paralysis (rare).
- Radioactive Iodine Therapy: Dry mouth, salivary gland inflammation, temporary changes in taste, and, rarely, an increased risk of secondary cancers.
- External Beam Radiation Therapy: Skin changes, fatigue, difficulty swallowing.
- Targeted Therapy: Side effects vary depending on the specific drug but can include fatigue, diarrhea, high blood pressure, and skin problems.
Q4. Will I need to take thyroid hormone medication after thyroid cancer treatment?
A4. If you have your entire thyroid gland removed (total thyroidectomy) or if your thyroid gland is destroyed by radioactive iodine therapy, you will need to take thyroid hormone replacement medication (levothyroxine) for the rest of your life.
Q5. Can thyroid cancer come back after treatment?
A5. Yes, thyroid cancer can recur, even years after treatment. Regular follow-up appointments with your doctor are essential to monitor for recurrence. Follow-up care typically includes physical exams, blood tests (thyroglobulin for differentiated thyroid cancers, calcitonin and CEA for medullary thyroid cancer), and imaging tests (ultrasound, radioactive iodine scans).
Conclusion: Early Detection and Treatment are Key
Thyroid cancer is often a treatable and manageable condition, especially when detected early. If you notice any lumps or swelling in your neck, or experience any other symptoms of thyroid cancer, see your doctor promptly. With appropriate treatment and follow-up care, most people with thyroid cancer can live long and healthy lives.