Thyroid cancer is not one disease. The main types arise from different cells, behave differently and are treated differently. Understanding which type you have is central to understanding your plan.
The two broad groups
Thyroid cancers are often divided into differentiated and non-differentiated types.
- Differentiated cancers — papillary and follicular — arise from the thyroid hormone-producing cells. They are the most common types and generally have a good outlook when treated appropriately.
- Non-differentiated and other types — medullary and anaplastic — arise from different cells or behave more aggressively.
Papillary thyroid cancer
Papillary cancer is the most common type. It arises from the follicular cells and tends to spread to lymph nodes in the neck rather than distant organs. It is usually treated with surgery, sometimes followed by radioactive iodine and thyroid hormone suppression.
Many papillary cancers are slow-growing, and small low-risk tumours may even be managed with active surveillance in selected cases.
Follicular thyroid cancer
Follicular cancer also arises from the hormone-producing cells but tends to spread through the bloodstream to distant sites such as the lungs or bones. Diagnosis often requires examining the whole nodule capsule, which is why a biopsy may be indeterminate.
Treatment is usually surgery followed by radioactive iodine in selected cases.
Medullary thyroid cancer
Medullary cancer arises from the C-cells, which make calcitonin. It is less common and is not treated with radioactive iodine in the same way as differentiated cancer. Surgery is the main treatment.
About a quarter of cases are associated with inherited syndromes such as MEN2, so genetic testing for RET mutations is important. Calcitonin is used as a tumour marker.
Anaplastic thyroid cancer
Anaplastic cancer is rare, aggressive and usually presents in older adults with a rapidly growing neck mass. It often requires urgent multidisciplinary assessment, surgery where feasible, radiotherapy and targeted therapy.
Less common types
Thyroid lymphoma, squamous cell carcinoma and metastases to the thyroid from other cancers also occur. Each requires specialist assessment.
How the type is determined
Diagnosis begins with ultrasound and fine-needle aspiration. Sometimes surgery is needed to obtain a definitive diagnosis, especially for follicular tumours. Staging then uses imaging to determine the extent of disease.
Why the type matters
The type determines:
- Whether radioactive iodine is useful
- Whether genetic testing is needed
- How closely follow-up should be conducted
- Which treatments are appropriate for advanced disease
If you have been diagnosed with thyroid cancer, ask your specialist to explain the type, the stage and the reasoning behind the treatment plan. That understanding makes follow-up far less confusing.