Types of Thyroid Cancer
Thyroid cancer doesn't occur in just one form. In fact, there are actually four distinct types of thyroid cancer, depending on where the cancerous cells develop. These different types of thyroid cancer span the whole range of cancer experience, from the tiny, slow-growing papillary form to the aggressive and fast-growing anaplastic form, a rare but deadly variation of thyroid cancer. Figuring out the type of cancer you have is the first step toward getting proper treatment.
Papillary Thyroid Cancer
The vast majority of thyroid cancers are papillary carcinomas. This type of thyroid cancer originates in the thyroid follicle cells and usually grows very slowly. In fact, papillary cancer grows so slowly that microscopic cells of this kind of cancer are found in 6 to 35 percent of autopsies, even though the person died of another cause.
In most cases, the cancerous cells occur in just one lobe of the thyroid, though they may occur in both lobes in 10 percent of the cases. Most people develop papillary thyroid cancer before age forty, and the majority of cases have no symptoms.
In some cases, a physician can detect papillary thyroid cancer just by feeling a lump in the thyroid gland. Some people may notice an enlarged lymph node or gland in their neck.
Little Orphan Annie was a comic strip created by Harold Gray in 1924. Annie was based on a character from a nineteenth-century poem by James Whitcomb Riley. It was the unusual appearance of her eyes — drawn as empty circles — that attracted the attention of medical experts, who noted the resemblance to thyroid cancer cells.
In any case, papillary thyroid cancer occurs within the nucleus of the thyroid cell. A healthy nucleus appears dark and round under a microscope. Cancerous nuclei show up as large, clear, circular areas that resemble what some describe as Little Orphan Annie eyes, after the 1920s comic-strip character. These cellular changes are called optically clear nuclei and are a key to diagnosing papillary thyroid cancer. Some nuclei may appear to have a line or groove through them, which is also an indication of papillary thyroid cancer.
Follicular Thyroid Cancer
The second most common kind of thyroid cancer is follicular thyroid cancer. This type of cancer accounts for about 20 percent of all cases of thyroid cancer. It is a more aggressive form of thyroid cancer and tends to occur in slightly older people. Although follicular thyroid cancer is less likely than papillary cancer to spread to the lymph nodes, it is more likely to enter the bloodstream and metastasize to other organs, such as the lungs, bladder, and liver.
Follicular thyroid cancer usually appears as a painless lump in the thyroid. But diagnosing follicular thyroid cancer is difficult. An FNA is generally unable to determine whether the lump is cancerous. Some characteristics of the nodule may appear suspicious, in which case, the doctor will do surgery to remove the nodule and have it examined by a pathologist for cancer.
Some people may develop a subtype of follicular thyroid cancer called Hurthle cell carcinoma, or oxyphil cell carcinoma. This type of cancer accounts for 4 percent of all thyroid cancers. In people with Hurthle cell carcinoma, the thyroid loses its ability to take up iodine, making it hard to use radioactive iodine in treating this form of cancer.
Another type of follicular thyroid cancer is insular thyroid cancer. This form of cancer is more aggressive than ordinary follicular thyroid cancer, but may still take up RAI.
Medullary Thyroid Cancer
Remember the parafollicular cells — also called C cells — tucked between the thyroid cells? As you might recall, these cells produce a hormone called calcitonin, which is involved in regulating calcium in your body. When cancer cells grow in the parafollicular cells, it is called medullary thyroid cancer.
These cancers account for 5 percent of all thyroid cancers. About 20 percent of people with this form of thyroid cancer inherited it from a parent. Anyone who has medullary cancer should have their parathyroid glands and adrenal medulla screened for tumors because medullary cancers may be associated with tumors in these glands, as described below.
Medullary thyroid cancer that has spread cannot be effectively treated with chemotherapy. It also can't be treated with RAI therapy since the cancerous cells don't take up iodine. The only option is a total removal of the thyroid and usually the lymph nodes as well.
Medullary cancer is relatively easy to diagnose. That's because the cells make calcitonin. Calcitonin then enters the bloodstream and can be detected by a simple blood test. There are essentially four types of medullary thyroid cancer (MTC):
Most cases of medullary thyroid cancer are called sporadic MTC. This form occurs in people who have no family history of the disease. It occurs most often in older adults and typically involves just one lobe.
This less common form occurs in each generation of a family. If it's the only type of cancer in the family, it's called isolated familial medullary thyroid carcinoma (FMTC). The familial forms of MTC often develop in childhood or early adulthood. Besides the isolated form, you could have one of two other subtypes, which involve tumors on other endocrine organs:
MEN stands for “multiple endocrine neoplasia,” which refers to tumors elsewhere in the endocrine system. If you have FMTC as well as tumors of the adrenal and parathyroid glands, you are said to have MEN2A. Tumors of the adrenal medulla, called pheochromocytomas, produce adrenaline, while tumors of the parathyroid gland cause elevated blood-calcium levels.
People with MEN2B have tumors of the adrenal gland but no problems with the parathyroid gland. Rather, they experience benign growths called neuromas on their tongue, the underside of the eyelids, and throughout the gut. People with MEN2B often have thick lips and thick eyelids as well as elongated fingers and toes.
Anaplastic Thyroid Cancer
Anaplastic thyroid cancer is relatively rare and accounts for about 2 percent of all thyroid cancers. Experts believe it develops out of an existing papillary or follicular cancer that, for unknown reasons, spins out of control. But it is an extremely aggressive form of cancer that rapidly invades the rest of the neck, then spreads to other parts of the body. The condition is also sometimes called undifferentiated thyroid cancer.
Former Chief Justice William Rehnquist died of anaplastic thyroid cancer in September 2005, just eleven months after he was diagnosed. Early on, he was given a tracheotomy — a hole in the windpipe — to alleviate an obstructed airway and to make breathing easier. The procedure is highly unusual in thyroid cancer and signaled the seriousness of his condition.
This form of thyroid cancer is more common in older people, and like the other kinds, occurs more often in women than men. But unlike other forms, the symptoms are abrupt and obvious. Patients often have trouble breathing and changes in their voice, such as hoarseness, caused by the fast-growing cancer pressing against their windpipe. Most patients will also see a large lump in the front of their neck.
Unfortunately, most people with anaplastic thyroid cancer will die within a few months of diagnosis, unless it is caught in its very early stages. Less than 10 percent of people who have it will survive more than five years.
Lymphomas are cancers that grow out of lymphocytes, the primary cell type in the body's immune system. Lymphomas usually start to grow in the lymph nodes. Thyroid lymphomas are rare and account for only about 3 percent of thyroid cancers. They usually occur in older adults who have Hashimoto's disease. Thyroid lymphomas usually begin as a fast-growing nodule.