Thyroid cancer
Thyroid cancer is a disease in which the thyroid cells become abnormal, grow
uncontrollably, and form tumors. Thyroid cancers are grouped into four types, based on how
the cell appears under the microscope. If left untreated, the cancer can spread to other
parts of the body.
General information about Thyroid cancer
The thyroid is a butterfly-shaped gland, located at the base of the throat. It has two
lobes, the left and the right. The thyroid gland makes hormones that regulate heart rate,
blood pressure, body temperature, and metabolism. The hormones produced by the thyroid
also affect the nervous system, muscles, and other organs, and play an important role in
regulating childhood growth and development. The thyroid uses iodine, a mineral found in
some foods, to make several of its hormones.
Diseases of the thyroid gland occur frequently, affecting millions of Americans. The
most common diseases are an overactive or an underactive thyroid gland. These conditions
are called hyperthyroidism (Grave's disease) or hypothyroidism. Sometimes, lumps or masses
may develop in the thyroid glands. Ninety-five percent of these lumps or nodules are
non-cancerous (benign), but all thyroid lumps should be taken seriously.
According to the estimates of the American Cancer Society, approximately 17,200 new
cases of thyroid cancer will occur in the United States in 1998. This disease accounts for
1% of all cancers.
A woman's risk of developing thyroid cancer is three times greater than a man's. Most
people who develop thyroid cancer are 50 years of age or older, but the disease can affect
teenagers and young adults.
Types of Thyroid cancer
Thyroid cancers are grouped into four types, depending on how the cells look under the
microscope. The types are papillary, follicular, medullary, and anaplastic thyroid
cancers. The cancers grow at different rates, so the aggressiveness of each cancer is
different.
Papillary cancer develops in the cells that produce thyroid hormones containing iodine.
It is a slow-growing cancer and can be treated successfully. About 60-80% of all thyroid
cancers are papillary cancers.
Follicular cancers also develop in the cells that produce iodine-containing hormones.
Many of the follicular cancers have a good cure rate, but if the cancer invades blood
vessels or grows into nearby structures in the neck, it may be difficult to control. About
30-50% of thyroid cancers are follicular cancers.
Medullary cancers develop in the parafollicular cells (also known as the C cells).
These cells produce a hormone called calcitonin, which does not contain iodine. These
cancers are more difficult to control because they have a tendency to spread to other
parts of the body. About 5-7% of all thyroid cancers are medullary cancers. Approximately
7% of medullary cancers are caused by the alteration (mutation) of a gene called the RET
gene; these cancers can be passed on in families.
Anaplastic cancer is the fastest growing of all thyroid cancers. The cells rapidly
spread to the different parts of the body. About 2% of all thyroid cancers are anaplastic
cancers. |