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Thyroid Cancer (cont.)

Thyroid Cancer Causes

There are four major types of thyroid cancers, listed below in order of decreasing frequency:

Papillary (includes follicular variant papillary thyroid carcinoma)

Papillary thyroid cancer (PTC) is the most common type of thyroid cancer and accounts for more than two-thirds of all thyroid cancers. There is a higher risk of developing this tumor in persons who have had previous head and neck radiation.

Most patients will not die from papillary thyroid cancer. They are considered low risk if:

  • They are younger than 45 years of age.
  • They have small tumors.
  • There is no invasion of surrounding structures and no metastasis (distant spread).

The spread of papillary thyroid cancer to lymph nodes may indicate recurrence, but it is not associated with a higher chance of death. The pattern of spread includes the lung, bone, and other soft tissue - usually in older people.

Follicular variant papillary thyroid cancer is a type of papillary thyroid cancer that has a survival rate similar to that of papillary thyroid cancer. Overall, papillary thyroid cancer is associated with a high survival rate.

Follicular (includes Hurthle cell and insular carcinoma)

Follicular thyroid cancer (FTC) occurs more in older patients compared to papillary thyroid cancer. The diagnosis of "malignancy" depends on the spread to local tissue and blood vessels. Like papillary thyroid cancer, the patient's age, size of tumor, and the extent that the tumor has spread can predict severity of disease.

Like papillary cancer, follicular cancer develops from the follicular cells and tends to grow slowly.

Variants of follicular thyroid cancer include insular carcinoma and Hurthle cell carcinoma of the thyroid. These tumors are less likely to concentrate radioactive iodine.

Medullary

Medullary carcinoma of the thyroid originates from the thyroid parafollicular, or C cells. C cells produce a hormone called calcitonin, which can be measured and used as a marker of medullary carcinoma. Medullary carcinoma can occur "sporadically" with no association, with other endocrine diseases, or may have a genetic basis when associated with familial medullary carcinoma or the multiple endocrine neoplasia syndromes (MEN). Multiple endocrine neoplasia syndromes are a group of endocrine diseases that result from an inherited gene mutation. With multiple endocrine neoplasia syndromes, the adrenal glands, the parathyroid glands, and the surface of the mouth may be affected in addition to the thyroid.

The manner of presentation is different when comparing the sporadic form usually presents with a solitary thyroid mass, whereas the hereditary form usually presents with bilateral thyroid masses in a multifocal fashion.

Medullary carcinoma can include multiple tumors in both lobes of the thyroid and frequently spreads to local lymph nodes, both in the neck and the mediastinum.

Patterns of spread usually occur late in the disease and involve the lungs, liver bones and adrenal gland.

Anaplastic thyroid cancer

Anaplastic thyroid cancer is a rare and fast-growing variant.

Some genetic mutations are related to some thyroid cancers. Damage to DNA can cause these gene mutations due to changes that occur during the natural aging process, radiation exposure, or radiation treatments (as used in the past for skin conditions and head and neck conditions).

Anaplastic thyroid cancer typically occurs in older patients and accounts for less than 5% of all thyroid cancers. One-fifth of patients may have a current history of another cancer, including a more common form of thyroid cancer. Anaplastic cancer is the most aggressive thyroid cancer. Local invasion and distant spread occur rapidly to other sites, including lymph nodes and the lungs.

Medically Reviewed by a Doctor on 6/26/2014
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