Thyroid Cancer

What thyroid cancer is

The thyroid makes hormones that control metabolism. Thyroid nodules are very common, found on ultrasound in up to half of adults, and more than 90 percent are benign. A small proportion are cancer.

Thyroid cancer has become more commonly diagnosed partly because ultrasound and CT detect small cancers that may never cause harm. It is about three times more common in women and is often diagnosed between ages 30 and 60.

Types of thyroid cancer

Papillary, follicular and oncocytic cancers are called differentiated thyroid cancers.

Risk factors

• radiation exposure to the head and neck, especially in childhood
• family history of thyroid cancer
• Hashimoto's thyroiditis, which is linked to a higher risk of papillary cancer and thyroid lymphoma
• inherited syndromes: multiple endocrine neoplasia type 2 (medullary cancer), familial adenomatous polyposis, Cowden syndrome
• female sex
• iodine deficiency (follicular cancer)
• obesity

Symptoms

Many thyroid cancers cause no symptoms and are found by chance. Possible signs:

• a lump or swelling in the front of the neck
• swollen lymph nodes in the neck
• hoarseness or voice changes that persist
• difficulty swallowing or breathing
• persistent cough not caused by a cold
• neck or throat pain, sometimes spreading to the ears
• diarrhea or flushing with advanced medullary cancer (from calcitonin)

Thyroid function tests are usually normal.

Diagnosis

1. Thyroid blood tests: TSH to check function
2. Ultrasound: assesses the nodule's size and features. Suspicious features include solid, darker (hypoechoic) appearance, irregular edges, microcalcifications and being taller than wide. Ultrasound risk systems such as ACR TI-RADS guide which nodules need biopsy
3. Fine-needle aspiration (FNA) biopsy: results are reported in Bethesda categories from benign to malignant
4. Molecular testing of indeterminate biopsies helps decide between surgery and monitoring
5. Calcitonin and CEA blood tests and RET gene testing for medullary cancer
6. Neck ultrasound of lymph nodes and sometimes CT before surgery

Treatment

Surgery

• Lobectomy: removing one side of the thyroid, often enough for small, low-risk cancers confined to one lobe
• Total thyroidectomy: removing the whole gland for larger or higher-risk cancers
• Lymph node dissection when nodes are involved

Active surveillance

For very small (under 1 cm), low-risk papillary cancers without spread, monitoring with regular ultrasound is an accepted alternative to immediate surgery for some people.

Radioactive iodine (RAI)

Given after total thyroidectomy for some intermediate- and high-risk differentiated cancers, to destroy remaining thyroid tissue and cancer cells. It is not used for medullary or anaplastic cancer.

Thyroid hormone therapy

Levothyroxine replaces thyroid hormone after total thyroidectomy and, at adjusted doses, can suppress TSH, which may help prevent recurrence in higher-risk cancers.

Advanced or resistant cancer

• targeted drugs such as lenvatinib, sorafenib, cabozantinib, and RET, BRAF or NTRK inhibitors for specific gene changes
• external beam radiation
• for anaplastic cancer, urgent multidisciplinary treatment combining surgery, radiation, chemotherapy and targeted drugs

Side effects of surgery

• low calcium from injury to the parathyroid glands, usually temporary
• hoarseness from injury to the recurrent laryngeal nerve, usually temporary
• lifelong thyroid hormone replacement after total thyroidectomy

Follow-up

Regular neck ultrasound and blood tests for thyroglobulin (for differentiated cancer) or calcitonin and CEA (for medullary cancer) detect recurrence. Most recurrences can be treated successfully.

Outlook

According to the American Cancer Society, 5-year relative survival for thyroid cancer is about 98 percent overall: over 99 percent when confined to the thyroid, about 98 percent with spread to nearby nodes, and about 55 percent with distant spread. Papillary cancer has the best outlook. Anaplastic cancer has a poor prognosis.

Frequently asked questions

What are the first signs of thyroid cancer?

The most common first sign is a painless lump in the front of the neck. Others include swollen neck lymph nodes, persistent hoarseness, difficulty swallowing and a feeling of pressure. Many thyroid cancers are found by chance on scans.

Is thyroid cancer curable?

Most thyroid cancers, especially papillary and follicular types, are highly curable with surgery and, when needed, radioactive iodine. Overall 5-year survival is about 98 percent. Anaplastic thyroid cancer is the exception and is much harder to treat.

Are thyroid nodules usually cancer?

No. Thyroid nodules are very common, and more than 90 percent are benign. An ultrasound and, when needed, a fine-needle biopsy determine which nodules need treatment.

Do I need my whole thyroid removed?

Not always. Small, low-risk cancers may be treated by removing one lobe, or in some cases by active surveillance. Larger or higher-risk cancers usually need total thyroidectomy. Your surgeon will discuss options based on size, spread and type.

Will I need thyroid hormone pills for life?

If your whole thyroid is removed, yes, you will need daily levothyroxine. After removal of one lobe, many people make enough hormone on their own, though some still need a small dose.