Thyroid cancer is cancer of the thyroid gland. This gland makes thyroid hormone, and it is found in the front of the neck. Thyroid gland tumors often appear as bumps in the neck, called nodules, usually in the thyroid gland. In most cases, thyroid nodules are not cancerous.

Thyroid Cancer
Thyroid tumor
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There are several types of thyroid cancer, including:

  • Papillary carcinoma (most common type)—It usually grows very slowly and often spreads to lymph nodes in the neck. If caught early, this type of thyroid cancer is often curable.
  • Follicular carcinoma (second most common type)—It usually stays in the thyroid gland, but can spread to other parts of the body, such as the lungs and bones. It does not usually spread to the lymph nodes. If caught early, this type of thyroid cancer is often curable.
  • Anaplastic carcinoma (rare form of thyroid cancer)—It quickly invades the neck and other parts of the body and is often fatal.
  • Medullary thyroid carcinoma (MTC)—This cancer develops from cells in the thyroid gland called C-cells. MTC often spreads to the lymph nodes, lungs, or liver before a thyroid nodule has been discovered. There are two types of MTC:
    • Sporadic MTC
    • Familial medullary thyroid carcinoma (FMTC)
  • Thyroid lymphoma (rare type of thyroid cancer)—Many cases occur in people who have a disease called Hashimoto's thyroiditis.

The cause is unknown.