The thyroid gland is the biggest gland in the neck. It is situated in the anterior (front) neck below the skin and muscle layers. The thyroid gland takes the shape of a butterfly with the two wings being represented by the left and right thyroid lobes which wrap around the trachea. The sole function of the thyroid is to make thyroid hormone. This hormone has an effect on nearly all tissues of the body where it increases cellular activity.
Thyroid cancer is a disease of the thyroid gland in which the cells become abnormal and form tumors. There are four different types of thyroid cancer: papillary, follicular, medullary, and anaplastic thyroid. The cancers grow at different rates, so the aggressiveness of each cancer is different. If left untreated, the cancer can spread to other parts of the body.
Papillary carcinoma: About 80% to 85% of thyroid cancers are papillary carcinomas. Papillary carcinomas develop from the thyroid follicle cells and typically grow very slowly. Usually they occur in only one lobe of the thyroid gland, but about 10% to 20% of the time both lobes are involved.
Follicular carcinoma: Follicular carcinoma is the next most common type of thyroid cancer. It is also sometimes called follicular cancer or follicular adenocarcinoma. Follicular cancer is much less common than papillary thyroid cancer, making up about 5% to 10% of thyroid cancers. It is more common in countries where people don’t get enough iodine in their diet. These cancers usually remain in the thyroid gland but can spread to other parts of the body, such as lungs and bone.
Anaplastic carcinoma: Anaplastic carcinoma is an uncommon form of thyroid cancer. It is believed to develop from an existing papillary or follicular cancer. It is an aggressive cancer that rapidly invades the neck, often spreads to other parts of the body, and is usually fatal. Anaplastic carcinoma is sometimes called undifferentiated thyroid cancer. Both of these names indicate that, under the microscope, they have very little, if any, similarity to normal thyroid tissue
Medullary thyroid carcinoma: Medullary thyroid carcinoma (MTC) is the only thyroid cancer that develops from the C cells of the thyroid gland. Sometimes this cancer can spread to lymph nodes, the lungs, or liver even before a thyroid nodule is discovered or a screening test is done.
The exact cause of thyroid cancer is not known; but it is more common in whites than in African Americans. Radiation was used in the 1950s and 1960s to treat acne and to reduce swelling in infections of the tonsils, adenoids and lymph nodes. It has been proven that this exposure is a risk factor for thyroid cancer. Recent studies prove that people who received radiation to the head and neck during their childhood have a higher than average chance of developing thyroid cancer.
Symptoms are rare so the lump is not usually painful. The symptoms of thyroid nodules are:
Several tests, including x-ray examination, transillumination of the gland, radioisotope scanning, needle biopsy and ultrasonic examination, may be performed by a doctor to determine size and location of the tumor and to determine whether it is non-cancerous (benign) or cancerous (malignant). If malignant, thyroid cancer can be diagnosed as one of four types. The most common type of thyroid cancer is papillary cancer, a slow-growing cancer that can usually be treated successfully. The second type, follicular cancer, also has a good cure rate. However, if follicular 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 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. Anaplastic cancer is the fastest growing of all thyroid cancers, however only 2% of all thyroid cancers are anaplastic.