Thyroid gland is a very important gland in the body which is located in the lower part of the neck, right above the sternum. This gland produces hormones that are vital to our well being. There are two kinds of cells in thyroid gland. Follicular cells, which produce thyroid hormones, that are essential for growth and development of all body tissues, and Parafolicullar cells which produce Calcitonin; a hormone that controls calcium levels in blood.
Thyroid nodule, refers to any solid lump in the thyroid gland. Most these nodules are benign and do not contain any cancer within them. However, any lump in the thyroid gland has to be studied properly to make certain of its nature. Incidence of thyroid cancer has been increasing in recent years, with roughly 13,000 Americans diagnosed with this illness ever year. This could be due to improved in diagnostic methods for early cancer or due to radiation therapy for treatment of other cancers. Certain types of thyroid cancer may remain silent and go undiagnosed for decades. The occult form is more commonly seen in Japanese. Thyroid cancer is rare in children, and the incidence rises with aging. Most these cancer are very slow growing and highly curable. A small group of patients may suffer from a very malignant form of this cancer, which is extremely difficult to treat.
CAUSES OF THYROID CANCER
Radiation therapy to the head and neck region was used in 1940-1960 for treatment of a variety of benign and not cancerous illness. This has shown to be the leading cause of thyroid cancer. The time frame from radiation to development of cancer is 10-30 years. radiation used in treatment of cancers of head and neck region can also cause this cancer. Any other incidental exposure to radiation, such as in Japan during World War II and following Chernobyl accident can also cause thyroid cancer.
Some genetic factors may play a role in development of thyroid cancer. Individuals with Gardner's Syndrome or Cowden's Disease are at higher risk of developing thyroid cancer. A higher incidence of this cancer is seen among residents or regions nearby active Volcanoes, in Hawaii, Philippines, Colombia, etc.
SIGNS AND SYMPTOMS
Most cases are diagnosed during work up of a thyroid lump. Since this gland is located near the skin, any lump or abnormalities in this gland can be detected very early. Most patients notice a lump or swelling in their neck and seek medical advice. At times, an examining physician may notice a lump and initiate he work up. Examination of thyroid gland should be part of any routine physical exam.
DIFFERENT TYPES OF THYROID
There are four basic kinds of thyroid cancer:
Papillary carcinoma, is the least aggressive form of thyroid cancer, which normally does not spread to distant sites. It is seen in younger adults, and can spread to lymph nodes in the neck. Mostly it involves one side of the thyroid and may vary in size.
Follicular carcinoma, is more aggressive than Papillary tumors. It does spread to distant sites, however, it can be easily cured or well controlled for decades. It is most commonly seen in older people, with highest incidence in 5th decade of life. They tend to metastasize to lungs and bone.
Medullary carcinoma, is the kind that is mostly familial and seen in association with other familial illnesses such as Gardner's Syndrome. This type of thyroid cancer is somewhat more aggressive than the two mentioned above and can spread to lymph glands in the neck and chest, as well as to lungs, liver and bones and other places. First degree relatives of all patients with this cancer should be monitored carefully. This cancer has a tendency to run in families and be associated with genetic abnormalities, for which they can be tested for. Family members should consider genetic counseling to determine their risk and possible work up for early detection of the cancer.
Anaplastic carcinoma is the most aggressive form of thyroid cancer which is hardly treatable and progresses and becomes fatal in matter of few months from the time of diagnosis. It grows rapidly in the neck and can spread to any organ in the body. Survivals over one year are very rare.
Other cancers that can be seen in thyroid are:
• Hurtle cell cancer which is a variant of follicular cancer
• Lymphomas that may originate or spread to thyroid gland
• Metastasis to thyroid gland form other cancer
STAGING
Once a diagnosis of the thyroid cancer is established, a thorough examination of the patients should be done to disclose crucial information. CT Scan or ultrasound of the neck can demonstrate the size of thyroid tumor, CT Scan of, chest and abdomen and a bone scan may be performed to determine the extent of the spread to other organs. Thyroid scan using a radioactive iodine study may also be used to determine the extent of the cancer.
TREATMENT
Treatment of thyroid cancer can be very complex. Three methods of treatment that may be used in conjunction with each other.
1. Surgery
2. Radioactive Iodine
3. Thyroid Suppression
Surgery is the first treatment and every patient with thyroid cancer. Surgery must be done by a thyroid surgeon, a surgeon who operates almost exclusively on thyroid gland. Thyroid is located nearby many crucial tissues in the neck and with rare exceptions, moat patients should have a complete removal of thyroid and lymph glands in the neck. Patients should seek appropriate referral to a major medical center for this surgery. Less experienced surgeon may perform an inadequate surgery and or cause major complications.
Radioactive Iodine: This agent is used in almost all patients undergoing surgery for thyroid cancer. The iodine is absorbed by the remaining thyroid tissue as well as thyroid cancer cell, resulting in lethal damage to these cells.
Thyroid Suppression: Following total thyroid ablation with surgery and radioactive iodine, patients need to be placed on hormone supplements. This treatment will result in inhibition of growth of reaming thyroid cells as well as cancer cells.
Chemotherapy is reserved for patients with very advanced disease as well as those with Anaplastic cancers. Few drugs are active in this condition. Adriamycin is among the most active drugs. Standard Radiation therapy can also be used in treatment of thyroid cancer, specially in Anaplastic cancers. Radiation can also be used to control the metastatic disease to the bones.
