Cancer is a group of many related diseases. All cancers begin in cells
, the body's basic unit of life. Cells make up tissues, and tissues make up the organs of the body.
Normally, cells grow and divide to form new cells as the body needs them. When cells grow old and die, new cells take their place. Sometimes this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor
Tumors can be benign or malignant.
Benign tumors are not cancer.
Usually, doctors can remove them. Cells from benign tumors do not spread to other parts of the body. In most cases, benign tumors do not come back after they are removed. Most important, benign tumors are rarely a threat to life.
Malignant tumors are cancer.
They are generally more serious. Cancer cells can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. That is how cancer cells spread from the original (primary
) tumor to form new tumors in other organs. The spread of cancer is called metastasis
There are four types of thyroid cancer:
- The most common type, making up 70-80% of all thyroid cancers. This type tends to grow slowly. It can spread to the lymph nodes, but even so, the outlook is generally good.
- This type makes up 10-15% of thyroid cancers and tends to occur in somewhat older patients than papillary. Like papillary cancer, it tends to grow slowly and can grow into lymph nodes in the neck. Follicular cancer is more likely than papillary cancer to grow into blood vessels and spread to distant areas, particularly the lungs and bones.
- About 5-10% of thyroid cancers, medullary cancer is more likely to run in families and be associated with other endocrine problems. Medullary thyroid cancer is the only thyroid cancer that can be diagnosed by genetic testing of the blood cells. A positive test for the RET proto-oncogene can lead to an early diagnosis.
- This is the most advanced and aggressive thyroid cancer. It is least likely to respond to treatment, but fortunately accounts for less than 5% of thyroid cancers.