There are four main types of thyroid cancer: papillary, follicular, medullary, and anaplastic. Papillary is by far the most common, accounting for 70% to 80% of all cases, while anaplastic is the rarest and most aggressive. Each type originates from different cells in the thyroid gland, grows at a different pace, and carries a very different prognosis.
Papillary Thyroid Cancer
Papillary thyroid cancer makes up the vast majority of thyroid cancer diagnoses. It develops from the follicular cells that produce thyroid hormone, tends to grow slowly, and has an excellent outlook. When caught before it spreads beyond the thyroid, the five-year survival rate for thyroid cancer overall is 99.9%, and papillary cases drive much of that statistic.
This type does have a tendency to spread to nearby lymph nodes in the neck, but even when it does, it usually responds well to treatment. Several subtypes exist, including the classic form, the tall cell variant, and the follicular variant. The tall cell variant carries a somewhat higher risk because it’s more likely to harbor a specific genetic mutation called BRAF V600E, which is found in 45% to 50% of papillary cases overall and in more than 70% to 80% of tall cell cases. That mutation can make the cancer less responsive to radioactive iodine therapy, a standard treatment for thyroid cancer.
Follicular Thyroid Cancer
Follicular thyroid cancer accounts for roughly 10% to 15% of thyroid cancers in the United States. Like papillary cancer, it arises from thyroid follicular cells, and the two are often grouped together as “differentiated” thyroid cancers because their cells still resemble normal thyroid tissue under a microscope. This matters for treatment: differentiated cancers typically take up iodine, which means radioactive iodine therapy can target them effectively.
Where follicular cancer differs is in how it spreads. Rather than moving to lymph nodes first, it tends to enter the bloodstream and travel to the lungs or bones. Distant metastasis occurs in 7% to 23% of patients. Follicular cancers frequently carry RAS gene mutations rather than BRAF mutations, which influences both behavior and treatment options.
Hürthle Cell Cancer
Hürthle cell cancer (also called oncocytic thyroid cancer) was historically grouped with follicular cancer but is now recognized as its own category. It’s more aggressive overall. Capsule invasion, spread beyond the thyroid, lymph node involvement, and distant metastasis are all more common in Hürthle cell cancer compared with standard follicular cancer. Metastasis rates run around 19.5% for Hürthle cell versus 12% for follicular. Another key difference: Hürthle cell tumors often don’t absorb radioactive iodine as reliably, so if the cancer doesn’t respond to radioactive iodine after the first round, continuing that treatment is unlikely to help.
Medullary Thyroid Cancer
Medullary thyroid cancer (MTC) accounts for just 1% to 2% of thyroid cancers, but it behaves quite differently from the others. It doesn’t come from the follicular cells that make thyroid hormone. Instead, it arises from parafollicular C cells, which produce a hormone called calcitonin. Because these cells don’t absorb iodine, radioactive iodine therapy doesn’t work for medullary cancer.
About 70% of medullary cases are sporadic, meaning they appear without a family connection. The remaining 30% are inherited, linked to mutations in a gene called RET. These hereditary cases are part of syndromes known as MEN2A and MEN2B (multiple endocrine neoplasia), which can also cause tumors in other glands. When MTC runs in a family, genetic testing can identify the RET mutation in relatives who haven’t yet developed cancer, sometimes prompting preventive surgery.
Calcitonin levels in the blood serve as a reliable marker for tracking this cancer after treatment. Rising calcitonin signals tumor growth, and the speed at which calcitonin levels double (the “calcitonin doubling time”) is actually a better predictor of how the disease will progress than standard imaging or clinical staging alone. In advanced cases, serial blood tests for calcitonin can detect changes before they show up on scans.
Anaplastic Thyroid Cancer
Anaplastic thyroid cancer is one of the most aggressive cancers in the human body. It accounts for a small fraction of thyroid cancers, but it is responsible for a disproportionate share of thyroid cancer deaths. Average survival is five to six months after diagnosis.
The cancer cells are described as “undifferentiated” because they no longer look or behave like thyroid cells at all. This means they don’t respond to radioactive iodine and grow extremely fast. The first sign is usually a hard, painful lump on the front of the neck that you can see and feel. As the tumor enlarges rapidly, it can press on surrounding structures, causing difficulty swallowing, breathing problems, hoarseness, a persistent cough, or vocal cord paralysis. When it spreads, which it often does early, it can cause bone pain, swollen lymph nodes, and neurological symptoms.
Anaplastic thyroid cancer frequently harbors BRAF and RAS mutations alongside additional genetic changes involving TP53 and the TERT promoter. In patients whose tumors carry the BRAF V600E mutation, a targeted drug combination has shown a 69% response rate, which represents a significant shift in treatment options for a cancer that was previously considered nearly untreatable.
Rare Types: Thyroid Lymphoma
Primary thyroid lymphoma is uncommon but worth knowing about. It originates from immune cells within the thyroid rather than thyroid cells themselves, and it tends to appear in older adults, with a median age at diagnosis around 65. People with a history of thyroiditis (chronic thyroid inflammation) appear to be at higher risk, and interestingly, those with thyroiditis also tend to have better outcomes if lymphoma does develop.
Five-year overall survival for primary thyroid lymphoma is about 74%, and ten-year survival is 71%. Aggressive subtypes respond best to combined treatment approaches, while indolent (slow-growing) lymphomas don’t necessarily benefit from more intensive therapy. Key factors that influence prognosis include age, tumor size, whether lymph nodes are involved, and the presence of systemic symptoms like fever, night sweats, or unexplained weight loss.
How Thyroid Nodules Get Evaluated
Most thyroid cancers are discovered when a nodule is found during a physical exam or imaging done for another reason. The standard next step is a fine-needle aspiration biopsy, where a thin needle extracts a small sample of cells for analysis. Results are reported using a six-category system that assigns a risk of malignancy to each category, ranging from benign (0% to 3% cancer risk) up to malignant (97% to 99% cancer risk).
Categories in the middle, where the biopsy is inconclusive, are where the decision-making gets more nuanced. A result labeled “follicular neoplasm” carries a 15% to 30% chance of being cancerous, while “suspicious for malignancy” lands at 60% to 75%. Molecular testing for mutations like BRAF, RAS, and TERT can help clarify these borderline results. The presence of a TERT promoter mutation alongside BRAF or RAS is particularly concerning because that combination is linked to radioactive iodine resistance and more aggressive behavior.
Survival by Stage
Thyroid cancer survival varies enormously depending on both the type and how far the cancer has spread at diagnosis. For all thyroid cancers combined, five-year relative survival is 99.9% when the cancer is confined to the thyroid, 98.1% when it has reached nearby lymph nodes, and 48.3% when it has spread to distant sites like the lungs or bones. Those overall numbers are heavily weighted toward papillary cancer, which is both the most common and the most survivable. Anaplastic cancer pulls the distant-stage number down significantly, while most people diagnosed with early-stage differentiated thyroid cancer can expect a normal lifespan.