OVERVIEW

What is thyroid cancer?

Thyroid cancer is a malignant tumor that occurs in the thyroid gland^[1]. It may be caused by genetics, radiation exposure, or a family history of thyroid cancer. It is also the most common malignant tumor in the endocrine system.

Thyroid cancer generally does not affect the secretion of thyroxine (T4) or triiodothyronine (T3). The main symptoms include neck lumps, difficulty breathing, and swollen lymph nodes in the neck. A few patients may also experience hoarseness or difficulty swallowing.

Most thyroid cancers are not highly malignant and rarely life-threatening. Total or near-total thyroidectomy, postoperative radioactive iodine-131 therapy, and TSH suppression therapy usually yield good treatment outcomes. Differentiated thyroid cancer has a favorable prognosis and low mortality, while anaplastic thyroid cancer has a poor prognosis^[2].

Is thyroid cancer common?

Yes. In 2019, the incidence of thyroid cancer in China was 14.6 per 100,000 people, meaning nearly 15 out of every 100,000 individuals are newly diagnosed with thyroid cancer each year^[3].

What is the thyroid gland?

The thyroid is an endocrine gland located in the front lower part of the neck, below the Adam's apple. It is butterfly-shaped and usually cannot be felt by touch. The thyroid produces thyroxine (T4) and triiodothyronine (T3), hormones that play a crucial role in maintaining body heat (temperature) and metabolic balance.

What are the types of thyroid cancer?

Thyroid cancer types are primarily classified based on pathological examination results, meaning the specific type cannot be confirmed without a hospital examination.

Broadly, thyroid cancer can be divided into differentiated and undifferentiated types. Differentiated thyroid cancer can be further classified into papillary carcinoma, follicular carcinoma, and medullary carcinoma.

The specific classifications are as follows:

1. Anaplastic carcinoma:

Accounts for 3%–8% of all thyroid cancers, mostly occurring in the elderly, with a slight predominance in women.

It grows rapidly and is painful, with high malignancy. About 80% of patients die within one year of diagnosis^[4].

2. Differentiated carcinoma:

• Papillary carcinoma: Accounts for 70%–90% of all thyroid cancers, mostly occurring in individuals aged 30–60, with a higher incidence in women. It may have a family history. Young patients with small tumors and no metastasis usually respond well to treatment^[4].
• Follicular carcinoma: Accounts for 10%–15% of all thyroid cancers, more common in the elderly and people in iodine-deficient regions. It is slightly more malignant than papillary carcinoma^[4].
• Medullary carcinoma: Accounts for 6%–8% of all thyroid cancers. It can produce calcitonin, detectable in the blood, and may have a family history. It can also be part of multiple endocrine neoplasia (MEN). It is highly malignant^[4].

Surgery is the primary treatment for differentiated thyroid cancer, supplemented by radioactive iodine, TSH suppression, or external radiation therapy.

Anaplastic thyroid cancer, the most aggressive type, has very limited treatment options. External beam radiation is mainly used for this type.

However, there is no need for excessive worry, as thyroid cancer generally has a high survival rate. Some thyroid cancers may be small (less than 1 cm) and may not progress, requiring only observation as advised by a doctor.

If diagnosed with thyroid cancer, active treatment under medical guidance offers a chance of recovery. Early-stage papillary thyroid cancer, in particular, may even be cured without recurrence.

Which department treats thyroid cancer?

Generally, thyroid cancer is treated in the thyroid and breast surgery department. If a hospital does not have a specialized department, patients may visit the general surgery or oncology surgery department.

If accompanied by abnormal thyroid hormone secretion (e.g., hyperthyroidism symptoms like rapid heartbeat, weight loss, or bulging eyes), treatment may also be needed in the endocrinology department.

SYMPTOMS

What are the manifestations of thyroid cancer?

In its early stages, thyroid cancer typically has no obvious symptoms and is often diagnosed when a painless neck lump or nodule is discovered.

However, as the cancer grows, it may cause hoarseness, neck and throat pain, difficulty swallowing, swollen lymph nodes in the neck, and may also be accompanied by symptoms such as facial flushing, rapid heartbeat, and persistent diarrhea.

When thyroid cancer metastasizes, it can lead to symptoms affecting other systems in the body, such as headaches, blurred vision, coughing, coughing up blood, chest pain, abdominal pain, jaundice (yellowing of the eyes, skin, or urine), and bone pain.

CAUSES

What are the causes of thyroid cancer?

The exact causes of thyroid cancer are still not fully understood. Possible risk factors include:

• History of head or neck radiation exposure or radioactive fallout contact during childhood: This significantly increases the risk of thyroid cancer, possibly due to radiation-induced gene mutations or the loss of tumor-suppressing gene function^[3].
• History of whole-body radiation therapy: Radiation exposure may cause gene mutations or impair cancer-suppressing genes, leading to thyroid cancer^[3].
• Personal or family history of thyroid cancer: Individuals with such histories have a higher probability of developing the disease^[3].
• Insufficient or excessive iodine intake: Both may lead to thyroid enlargement and eventually thyroid cancer^[5].
• Gender: Women are more likely to develop thyroid cancer than men^[1].

If you have the above risk factors and notice a progressively enlarging, hard lump in your neck, thyroid cancer should be suspected, and medical attention should be sought promptly.

Who is more likely to develop thyroid cancer?

• Individuals with a family history of thyroid cancer: These people have a higher probability of developing the disease.
• Those frequently exposed to ionizing radiation: For example, radiology workers who are regularly exposed to ionizing radiation are more likely to develop thyroid cancer.
• Women: The incidence of thyroid cancer is higher in women than in men in China, making women more susceptible.
• People with excessive or insufficient iodine intake: These individuals may experience excessive secretion of thyroid-stimulating hormone by the pituitary gland, leading to goiter and eventually thyroid cancer. The World Health Organization defines a urinary iodine median of 100–199 μg/L as the optimal range, below 100 μg/L as insufficient iodine intake, and above 199 μg/L as excessive iodine intake^[5].

Is thyroid cancer hereditary?

It has a genetic predisposition but does not necessarily develop.

With advances in science, it has been discovered that the development of thyroid cancer is related to genetic factors, particularly certain specific types (such as medullary thyroid carcinoma), which have a hereditary component^[3].

DIAGNOSIS

What tests are needed to diagnose thyroid cancer?

1. Laboratory tests:

   • Routine tests: Including blood tests and liver/kidney function tests to assess the patient's general condition and determine if corresponding measures are needed.
   • Thyroid hormone tests: Measuring levels of thyroxine (T4), triiodothyronine (T3), free T4, free T3, and thyroid-stimulating hormone (TSH) in the blood to evaluate thyroid function.
   • Thyroid autoantibody tests: Used to monitor whether the tumor has recurred or metastasized after surgery.

2. Imaging tests:

   • Ultrasound: Easily detects nodules, their number, relationship with surrounding tissues, and potential metastasis.
   • CT scan: Less significant for diagnosis but useful for evaluating rapidly growing thyroid cancer's invasion of other organs.
   • Thyroid scintigraphy: Typically performed postoperatively with radioactive 131I to assess residual thyroid size and function.

Are thyroid cancer and thyroid nodules the same disease?

Thyroid nodules refer to lumps within the thyroid gland, a common manifestation of thyroid diseases rather than a specific condition. Thyroid nodules can be benign or malignant, with only about 5–15% being malignant (thyroid cancer)^[1]. Nodules confirmed as non-cancerous are benign.

How is thyroid cancer screened?

Thyroid cancer screening primarily evaluates risk factors such as medical history, family history of thyroid cancer, radiation exposure, thyroid palpation, and thyroid function test results. High-risk patients undergo neck ultrasound screening.

How is thyroid cancer diagnosed?

Definitive diagnosis relies on pathological evidence (especially postoperative pathology). Preoperative diagnosis mainly depends on ultrasound-guided fine-needle or core-needle biopsy. However, fine-needle aspiration may occasionally disagree with postoperative pathology and is not the gold standard.

What is a thyroid fine-needle aspiration?

Thyroid fine-needle aspiration cytology (FNAC) involves extracting cells from thyroid tissue using a thin needle for pathological examination. The procedure is typically performed under imaging guidance (e.g., ultrasound).

How to briefly understand a thyroid FNAC report?

The report generally includes two parts: a description of cell morphology and an assessment of malignancy risk.

Malignancy risk is graded into 5 levels:

• Grade 1: Benign
• Grade 2: Atypical or follicular lesion
• Grade 3: Follicular neoplasm or suspicious follicular neoplasm
• Grade 4: Suspicious for malignancy
• Grade 5: Malignant

Grades 1–3 suggest benign tendencies, while grades 4–5 indicate malignant tendencies.

TREATMENT

What are the treatment options for thyroid cancer?

Treatment for thyroid cancer primarily includes: surgical treatment, TSH suppression therapy, radioactive iodine-131 therapy, and targeted drug therapy.

Targeted drug therapy: Commonly used drugs like dabrafenib can inhibit tumor proliferation and are suitable for advanced differentiated thyroid cancer patients unresponsive to radioactive iodine-131 therapy. Possible side effects include rash, diarrhea, and elevated blood pressure^[3].

Radiation therapy: Used for medullary thyroid carcinoma and anaplastic thyroid carcinoma, typically combined with post-surgical treatment^[3].

Chemotherapy: Common drugs include paclitaxel and carboplatin, mainly for anaplastic thyroid carcinoma. Side effects may include facial itching and difficulty breathing^[3].

Surgical treatment: Different surgical approaches are chosen based on the type of thyroid cancer.

• Papillary carcinoma: Partial lobectomy or total thyroidectomy may be performed, with lymph node dissection as needed^[6].
• Follicular carcinoma: Similar to papillary carcinoma, with iodine-131 therapy for distant metastases^[6].
• Medullary carcinoma: Total or near-total thyroidectomy with lymph node dissection is recommended^[6].
• Anaplastic carcinoma: At diagnosis, this type often has distant metastases, making complete surgical removal difficult. Only a small subset with limited metastases may undergo total thyroidectomy^[6].

What are the types of thyroid cancer surgery?

Thyroid surgeries are mainly divided into two categories:

• Total/near-total thyroidectomy with or without lymph node dissection: Complete or partial removal of the thyroid, with lymph node dissection if cancer has spread^[1].
• Thyroid lobectomy: Removal of one thyroid lobe, recommended for patients meeting all the following criteria: ① No history of neck radiation; ② No distant metastases (e.g., to lungs); ③ No extrathyroidal invasion; ④ No other high-risk pathological features; ⑤ Tumor diameter <1 cm^[1].

Currently, the former approach is more commonly used to prevent recurrence.

What is TSH suppression therapy?

For differentiated thyroid cancer patients, long-term thyroid hormone (levothyroxine or thyroid tablets) therapy is required post-surgery to meet physiological needs and reduce recurrence risk by suppressing TSH^[6].

What is radioactive iodine-131 therapy?

Iodine-131 is a radioactive isotope that emits radiation to kill cells. The thyroid absorbs iodine more efficiently than other organs, making iodine-131 effective for targeting residual or metastatic differentiated thyroid cancer cells. It is typically administered 6–12 weeks post-surgery after a low-iodine diet. Contraindications include pregnancy, breastfeeding, or inability to follow safety guidelines^[6].

Is surgery always necessary for thyroid cancer?

Surgical removal is recommended for all diagnosed thyroid cancers. It eliminates the primary tumor and helps determine cancer type, stage, and lymph node involvement, improving prognosis.

Is long-term medication needed after thyroid cancer surgery?

Yes. Most patients require lifelong thyroid hormone replacement to maintain TSH levels within the target range due to reduced thyroid function post-surgery^[6].

What complications or side effects may occur after thyroid surgery?

• Recurrent laryngeal nerve injury: Causes hoarseness or choking while drinking due to surgical manipulation or tumor adhesion^[3].
• Hypoparathyroidism: Often occurs after total thyroidectomy, leading to numbness or spasms in hands/feet^[3].
• Infection: Possible in clean surgical wounds, presenting as fever or pain at the incision site^[3].

How are post-surgical complications treated?

• Hypoparathyroidism: Temporary cases are managed with calcium supplements, while permanent cases require lifelong vitamin D and calcium^[3].
• Hoarseness/difficulty speaking: Usually temporary due to nerve edema during surgery and resolves over time.

Is chemotherapy needed after thyroid cancer surgery?

Differentiated thyroid cancer is generally chemotherapy-resistant, but it may be used palliatively in advanced cases unresponsive to other treatments. Medullary thyroid carcinoma responds better to targeted therapy^[2].

Can thyroid cancer be completely cured?

Early treatment increases cure likelihood. Most early-stage differentiated thyroid cancers have excellent prognoses, while distant metastases significantly reduce survival rates.

How often should thyroid cancer patients follow up post-treatment?

For at least five years post-surgery, serum TSH and thyroglobulin (Tg) levels should be checked every 3–6 months. Ultrasound, CT/MRI, or whole-body iodine scans may be performed as needed.

DIET & LIFESTYLE

What should thyroid cancer patients pay attention to in daily life?

They should cultivate healthy lifestyle habits, such as maintaining a balanced diet, exercising regularly, quitting smoking and alcohol, and keeping a positive mindset.

Additionally, some thyroid cancer patients require long-term high-dose thyroid hormone replacement after surgery. They should be vigilant about potential side effects, including heart disease and osteoporosis, and follow medical advice for regular check-ups, including assessments of heart function and bone density.

Patients undergoing 131I therapy should avoid prolonged close contact with pregnant women and children for a certain period after discharge.

What dietary precautions should thyroid cancer patients take?

• If radioactive 131I therapy is not required after surgery, there are no specific dietary restrictions—maintaining a healthy, balanced diet is sufficient:
• Use less salt and oil in cooking, avoid high-sodium seasonings, and limit intake of pickled vegetables and cured meats.
• Balance meat and vegetable intake, prioritizing white meats like chicken, duck, and fish while reducing fatty meats. Eggs and dairy are important sources of protein and other nutrients.
• Vegetarians can increase intake of beans and soy products for protein.
• Eat more fruits and vegetables.
• Avoid alcohol as much as possible.
• If radioactive 131I therapy is planned after surgery, follow a low-iodine diet for at least 1–2 weeks beforehand, avoiding iodized salt and iodine-rich foods like seaweed and kelp.

Can thyroid cancer patients get pregnant and have children?

Yes.

There is no evidence that pregnancy increases the risk of thyroid cancer recurrence. However, radioactive 131I therapy for differentiated thyroid cancer may cause birth defects, so patients who undergo this treatment should use contraception for 6–12 months before planning pregnancy.

PREVENTION

How to Prevent Thyroid Cancer?

This disease is difficult to prevent because the exact cause of thyroid cancer is still unclear. However, the following measures may help reduce the risk:

• Regarding radiation exposure, which may cause thyroid cancer: Avoid prolonged exposure to radiation and follow medical guidance for protection.
• For those with a family history of thyroid cancer: Annual thyroid checkups are recommended for early detection and prevention.
• In daily life, quit smoking and alcohol, maintain a regular sleep schedule, exercise regularly, and boost immunity.

How to Detect Thyroid Cancer Early?

In addition to regular checkups, learning self-examination techniques can help identify thyroid abnormalities early.

Stand in front of a mirror, slightly raise your chin, and tilt your head back to fully expose your neck. You can also place one hand behind your neck for support or lean against a wall. Observe the thyroid area in the mirror for swelling, asymmetry, or enlargement on one side.

Press your index, middle, and ring fingers together and gently glide them along both sides of your neck from top to bottom to check for nodules or swelling. Then swallow and note which part of your neck moves with the action.

After locating the thyroid, observe in the mirror whether any lumps move up and down when swallowing. Gently feel the thyroid area for hard nodules, soft bumps, or unusual masses. If abnormalities are found, consult a doctor promptly.