Disease Description (Causes and Symptoms)
- Definition summary: A malignant tumor occurring in the thyroid gland. Histological types include papillary, follicular, medullary, and undifferentiated (anaplastic) carcinoma.
- Main causes/risk factors: The cause is unknown in most cases. Known risk factors include radiation exposure to the neck (dose-dependent), familial genetic syndromes (especially RET mutations associated with medullary carcinoma), a history of previous thyroid disease, and iodine intake status.
- Pathophysiology (brief): Growth patterns and routes of metastasis differ according to the cell of origin (thyroid follicular cells vs. C cells). Papillary and follicular types generally have a relatively good prognosis and may metastasize to lymph nodes or through the bloodstream; medullary carcinoma originates from C cells and is characterized by hematogenous metastasis and elevated endocrine markers (calcitonin); anaplastic carcinoma progresses rapidly.
- Main symptoms: A painless nodule (lump) in the neck may be palpable, along with rapid growth of the nodule, difficulty swallowing, difficulty breathing, and voice changes (vocal cord paralysis or hoarseness). Suspicion of malignancy increases when the nodule is large (≥4 cm) or solitary. Many cases are asymptomatic in the early stages.
Treatment Methods and Precautions
- Surgery: The standard first-line treatment is resection. In many cases (excluding microcarcinoma measuring 1.0 cm or less among early papillary carcinomas), total thyroidectomy is often recommended (because multifocal lesions are common and it facilitates subsequent surveillance and iodine treatment).
- Radioactive iodine (131I) therapy: Administered within 4–8 weeks after surgery to remove remaining thyroid tissue and micrometastases. A response rate of approximately 50–80% has been reported for recurrence or metastasis of papillary and follicular carcinoma. It is effective only when the thyroid has been completely removed surgically.
- Thyroid hormone replacement and TSH suppression: Lifelong thyroid hormone (levothyroxine) use is required. To suppress recurrence, TSH may be maintained at a low level, adjusted according to individual risk.
- Reoperation, external radiation, and systemic therapy: In cases of recurrence or metastasis that does not respond to radioactive iodine, reoperation, external radiation therapy (especially for locally advanced or anaplastic carcinoma), targeted therapy (e.g., kinase inhibitors such as lenvatinib and sorafenib for RAI-refractory advanced cancer), or clinical trials may be considered. Medullary carcinoma is not sensitive to radioactive iodine, so surgery is the main treatment, with targeted therapy used in some cases.
- Complications and precautions: Possible complications include recurrent laryngeal nerve injury after surgery (voice changes), hypocalcemia due to hypoparathyroidism (numbness and spasms), bleeding and infection, and hypothyroidism if lifelong hormone replacement is not taken as prescribed. TSH suppression strategies increase the risk of osteoporosis and atrial fibrillation, so caution is needed in older adults and patients with cardiovascular disease. Treatment and hormone targets need to be adjusted when planning pregnancy.
Checklist Before an Outpatient Visit (Including Items to Prepare and Sample Questions)
- Items to prepare (bring with you)
- List of medications and supplements currently being taken (including doses and administration times)
- Previous test results (ultrasound images, fine-needle aspiration results, thyroid function tests, radioactive iodine tests, chest X-rays/CT/PET, etc.) or CDs/films
- Records of previous surgeries and hospitalizations, as well as anesthesia history and previous surgical complications
- Family history (thyroid cancer, endocrine-related cancers, etc.) and history of radiation exposure (whether the neck was exposed to radiation during childhood)
- Symptom diary (when symptoms began and how they have changed—changes in the size of the neck lump, breathing, swallowing, or voice changes, etc.)
- For women, the date of the most recent menstrual period and pregnancy status (a pregnancy test may be necessary)
- Items that are helpful to record during the outpatient visit
- Whether the nodule is palpable and its growth rate (based on the patient's observations)
- The degree of voice changes, shortness of breath, and difficulty swallowing (onset and aggravating factors)
- Materials to present to the doctor in advance during the outpatient visit
- Recent ultrasound (or previous images if an examination is requested), and the fine-needle aspiration (FNA) pathology report
- Recent blood tests (TSH, free T4, antibodies, and calcitonin if necessary)
Examples of General Questions to Ask the Doctor
- What is the exact histological type of this disease (papillary/follicular/medullary/anaplastic)? What is the prognosis for that type?
- In my case, is total thyroidectomy or partial thyroidectomy recommended, and why?
- Is radioactive iodine therapy necessary? If so, when should it be performed and what side effects can be expected?
- What is the target TSH level for the thyroid hormone that I will need to take for life? How will the risks of side effects, such as osteoporosis and heart problems, be managed?
- Which tests (such as thyroglobulin, ultrasound, and radioactive iodine whole-body scanning) will I need for recurrence surveillance, and at what intervals?
Examples of Disease-Specific Questions
- (For those scheduled for surgery) Based on the size of my nodule/cancer and the degree of lymph node involvement, is total thyroidectomy absolutely necessary? Is follow-up alone after partial thyroidectomy possible?
- (When medullary carcinoma is suspected or confirmed) What are my calcitonin and CEA levels? Is RET genetic testing (to determine whether it is familial) recommended?