The thyroid gland is located in the front of the neck and is shaped like a bow tie. Hormones secreted by the thyroid gland regulate heart rate, body temperature, blood pressure and weight. Persistent lumps in the neck, trouble swallowing or breathing, and a hoarse voice could be signs of thyroid carcinoma, or cancer. Blood work, ultrasound or magnetic imaging, and biopsy are diagnostic. Cancer cells are differentiated by where they originate, how they appear under a microscope and how they behave in the body. There are five main types of thyroid cancer.
Papillary
According to J. L Gluckman and J.T. Johnson, authors of "Carcinoma of the Thyroid," papillary carcinoma is the most common form of thyroid malignancy. In the United States, 60% to 80% of all thyroid cancer is papillary; it affects women three times more often than men and is more common in people over the age of 40. When detected early, with lesions smaller than a half inch, it has a cure rate and 10-year survival rate of more than 90%. This slow-growing carcinoma may spread to lymph nodes in the neck but very rarely metastasizes, or spreads, to bone and lung tissue. Exposure to ionizing radiation in childhood is a major risk factor for this type of thyroid cancer. Between 1940 and 1960, children in the U.S. were treated with radiation for enlarged tonsils, according to The American Thyroid Association.
Follicular
Accounting for 5% of all thyroid malignancies, follicular cancer cells typically are minimally invasive and have only a slightly poorer prognosis than papillary cancer. When follicular carcinoma is not detected early, however, it may metastasize to the lung, bone, brain and liver. According to Gluckman and Johnson, the risk of follicular thyroid carcinoma is higher in regions where iodine deficiency is common.
Medullary
Medullary thyroid cancers occur primarily in men and comprise approximately 5% of all thyroid malignancies. One type, familial medullary thyroid carcinoma, is an inherited disorder. Medullary cancer is the only thyroid carcinoma that can be diagnosed by genetic testing. Tumors may appear at any age, including childhood, but most occur in men in their early 30s. The American Thyroid Association encourages screening of all at-risk family members. Those who test positive can be cured surgically.
Anaplastic
Anaplastic thyroid carcinoma is also known as undifferentiated carcinoma because the tumor cells may have some features of papillary or follicular carcinoma but behave much more aggressively. A rapidly enlarging mass in the neck with compression and paralysis of vocal cords is symptomatic and almost always fatal. Those who are over 50 years old and have a long history of thyroid disease are most at risk for this rare type of thyroid cancer. The American Thyroid Association estimates that less than 5% of patients with thyroid cancer have the anaplastic type.
Lymphomas
Gluckman and Johnson categorize 5% of thyroid malignancies as primary thyroid lymphomas, noting that it is often confused with the anaplastic type. Microscopic staining and a tumor that is softer on palpation help doctors to tell the difference. Lymphomas are more common in women over age 60. With chemotherapy and radiation treatment, primary thyroid lymphomas have a cure rate of 50% to 80% .
References
- "Carcinoma of the Thyroid"; JL Gluckman and JT Johnson, 1999
- The American Thyroid Association: Childhood Head and Neck Irradiation FAQ
