Thyroid cancer is a malignant tumor arising from cells of the thyroid gland. The main types are papillary, follicular, medullary and anaplastic thyroid cancer. Many thyroid cancers are highly treatable, especially when detected early, although anaplastic thyroid cancer can be aggressive.
Thyroid cancer begins in cells of the thyroid gland in the front of the neck. The four main types are papillary, follicular, medullary and anaplastic. Papillary cancer is the most common. Papillary and follicular cancers are generally differentiated thyroid cancers and are often highly treatable. Medullary cancer arises from parafollicular C cells, while anaplastic cancer is uncommon and highly aggressive.
The thyroid is a butterfly-shaped endocrine gland in the front of the lower neck. It has right and left lobes connected by an isthmus and lies near the trachea, esophagus, recurrent laryngeal nerves and parathyroid glands.
Thyroid cancer begins when thyroid follicular cells or parafollicular C cells acquire genetic alterations that disrupt normal cell growth and survival. The resulting abnormal cells may form a thyroid nodule and can eventually invade surrounding tissues or spread.
Abnormal thyroid cells acquire genetic changes that allow uncontrolled growth. The tumor may remain confined to the thyroid, spread to nearby lymph nodes or invade surrounding neck structures. Some thyroid cancers can spread through blood vessels to distant organs.
Thyroid cancer is primarily classified as papillary, follicular, medullary or anaplastic. Papillary and follicular cancers arise from follicular cells. Medullary cancer arises from parafollicular C cells. Anaplastic cancer represents an undifferentiated, rapidly growing form.
The four major types are papillary, follicular, medullary and anaplastic thyroid cancer. Papillary is the most common. Papillary and follicular cancers are differentiated thyroid cancers. Medullary thyroid cancer is a neuroendocrine cancer arising from C cells. Anaplastic thyroid cancer is rare and aggressive.
Thyroid or neck lump
Neck swelling
Enlarged cervical lymph nodes
Persistent hoarseness or voice change
Difficulty swallowing
Difficulty breathing
Neck discomfort or pain
Pressure sensation in the neck
Many thyroid cancers cause no symptoms
Rarely, symptoms related to advanced or metastatic disease
There is no single cause of thyroid cancer. Risk can be associated with ionizing radiation exposure, certain inherited genetic conditions, family history and specific molecular changes. Many thyroid cancers occur without an identifiable preventable cause.
Previous exposure to ionizing radiation
Childhood or young-age radiation exposure
Family history of thyroid cancer
Multiple endocrine neoplasia type 2
Familial medullary thyroid cancer
Inherited RET pathogenic variants
Female sex
Increasing age for some thyroid cancer types
Previous radiation treatment to the head or neck
Diagnosis commonly begins with thyroid ultrasound and assessment of a suspicious nodule. Fine-needle aspiration may be performed for appropriate nodules. Thyroid function tests, neck imaging, molecular testing and surgical pathology may provide additional information.
Palpable thyroid nodule
Neck swelling
Enlarged cervical lymph nodes
Persistent hoarseness
Difficulty swallowing
Difficulty breathing
Neck tenderness or discomfort
Evidence of recurrent disease on follow-up examination
TSH blood test
Free T4 when clinically indicated
Serum thyroglobulin for selected differentiated thyroid cancer follow-up
Anti-thyroglobulin antibodies when monitoring thyroglobulin
Calcitonin for suspected or known medullary thyroid cancer
CEA in selected medullary thyroid cancer cases
Serum calcium after thyroid surgery
Molecular or genetic testing when indicated
Routine blood chemistry tests when required for treatment
Thyroid and neck ultrasound
Radioactive iodine thyroid scan in selected differentiated thyroid cancers
CT of the neck or chest when indicated
MRI in selected cases
PET/CT for selected advanced or recurrent disease
Post-treatment whole-body iodine imaging when appropriate
Fine-needle aspiration biopsy
Molecular testing of thyroid tumor tissue
RET genetic testing for suspected hereditary medullary thyroid cancer
Laryngoscopy when vocal-cord function needs assessment
Pathology review by an experienced thyroid pathologist
Benign thyroid nodule
Thyroid cyst
Hashimoto thyroiditis
Subacute thyroiditis
Multinodular goiter
Parathyroid lesion
Reactive cervical lymph node
Metastatic cancer from another primary site
Thyroid cancer staging depends on the cancer type and age at diagnosis. Papillary and follicular cancers use different stage groupings according to age, while medullary and anaplastic cancers have their own staging systems. TNM assessment considers the primary tumor, regional lymph nodes and distant metastases.
Staging or grading systems differ between diseases. The information here is educational and should be interpreted by a qualified healthcare professional in the context of the individual case.
Treatment depends on cancer type, size, stage, molecular features and patient factors. Options include lobectomy, total thyroidectomy, lymph-node surgery, radioactive iodine, thyroid-hormone therapy, external-beam radiation, targeted therapy and selected systemic treatments. Active surveillance may be appropriate for selected low-risk papillary thyroid cancers.
Levothyroxine for thyroid hormone replacement
Thyroid-hormone suppression therapy when clinically indicated
Radioactive iodine for selected differentiated thyroid cancers
Tyrosine kinase inhibitors for selected advanced thyroid cancers
RET-targeted therapy for selected RET-altered cancers
Other targeted medicines selected according to tumor molecular findings
Analgesics and supportive medicines when required
Medicines listed here are for educational information only. Do not start, stop, or change a medicine without professional medical advice.
Complications can result from the cancer itself or treatment and may include airway or swallowing problems, vocal-cord nerve injury, low calcium after surgery, hypothyroidism, recurrent disease and distant metastases.
Sudden or severe difficulty breathing
Rapidly enlarging neck swelling
Severe difficulty swallowing or inability to swallow
Severe voice change associated with breathing difficulty
Symptoms suggesting severe low calcium such as muscle spasms or seizures
Severe symptoms caused by advanced metastatic disease
If symptoms are severe, rapidly worsening, or life-threatening, seek emergency medical care immediately.
Many differentiated thyroid cancers have a favorable prognosis, particularly when diagnosed early. Prognosis is influenced by cancer type, age, stage, tumor size, lymph-node or distant spread, completeness of surgical removal and response to treatment.
Survival statistics describe outcomes in groups of people and cannot predict exactly what will happen to one individual. Prognosis depends on factors such as cancer stage, tumor biology, treatment response, overall health, and follow-up.
Thyroid cancer can occur at any age but is more frequently diagnosed in women than men. Papillary thyroid cancer is the most common type. Incidence and detection vary by population, access to imaging and diagnostic practices.
There is no proven general prevention strategy for all thyroid cancers. Avoid unnecessary ionizing radiation exposure, follow appropriate occupational and medical safety measures, and seek specialist advice when there is a strong hereditary cancer history.
What type of thyroid cancer do I have?
What is my stage and risk category?
Do I need a fine-needle aspiration biopsy?
Do I need a lobectomy or total thyroidectomy?
Are lymph nodes involved?
Do I need radioactive iodine treatment?
Will I need lifelong thyroid hormone replacement?
Should my tumor undergo molecular testing?
Should I have genetic testing for RET or another inherited mutation?
Which symptoms should make me seek urgent medical care?
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