What are the four types of thyroid cancer?

Thyroid cancer can be described as differentiated thyroid cancer or medullary thyroid cancer. The first group holds three levels. Well-differentiated tumors are papillary and follicular thyroid cancer. Next come poorly differentiated tumors. Last are undifferentiated tumors, known as anaplastic thyroid cancer. The types differ in how aggressive they are.

Papillary and follicular cancers are the well-differentiated ones. Their cells still look and act much like normal thyroid cells. They can be treated, and they can usually be cured.

Anaplastic cancer sits at the far end. It grows fast and spreads fast. The chance of recovery is poorer. It is not common. It is always called stage IV, split into IVA, IVB, and IVC by how far it has spread. That is unusual. For most cancers, stage IV means the cancer has reached distant organs. Here the label reflects how the disease acts.

Medullary thyroid cancer is a different animal. It is a neuroendocrine tumor. It starts in the C cells of the thyroid. C cells make calcitonin, a hormone that helps keep blood calcium at a healthy level.

Why the type decides the treatment

Take radioactive iodine, often shortened to RAI.

Thyroid tissue is the only tissue in the body that takes up iodine. That single fact makes a clean treatment possible. You swallow the iodine. It travels to thyroid tissue and thyroid cancer cells. It destroys them, and it spares everything else. Follicular and papillary cancers are sometimes treated this way.

Medullary cancer does not fit that logic. It starts in C cells, not in the cells that take up iodine. Anaplastic cancer no longer acts like normal thyroid tissue either. Both are treated on other lines. So when people call thyroid cancer "the good cancer," they mean papillary disease. They do not mean these two.

The family thread in medullary cancer

Medullary cancer is the type most tied to genes. A change in the RET gene can pass from parent to child and cause it. The NCI names three related conditions. They are familial medullary thyroid cancer, multiple endocrine neoplasia type 2A, and multiple endocrine neoplasia type 2B.

A medullary diagnosis is therefore never only about you. Relatives may need RET testing. A positive result changes what gets watched, and when.

What raises risk

The NCI lists age 25 to 65, and being female. It lists radiation to the head or neck. It lists a history of goiter, and a family history of thyroid disease. It also lists certain genetic conditions and Asian ancestry.

What to ask for

Get the exact type in writing from your pathology report. The four names lead to four different conversations. Searching "thyroid cancer" alone will hand you numbers that may not apply to you at all.

If it is medullary, ask about RET testing for you and your family. If it is anaplastic, ask how fast treatment can start. Ask about referral to a center that sees this cancer often. Speed matters more here than with the other types.

If it is papillary or follicular, ask whether RAI is part of the plan. Ask what your thyroid hormone pills will look like afterward, since the thyroid you remove is the gland that made them.