Learning about Thyroid Cancer Risks

In the year 2000, the Thyroid Cancer Survivors’ Association initiated and sponsored a Thyroid Cancer Awareness program for one week every September. This was expanded in 2003 to include the entire month of September as a worldwide program. That is notable because there has been an increased incidence in the diagnosis of thyroid cancer in the last 25 years, not only in the United States but worldwide. 

Thyroid cancer accounts for slightly more than 1 percent of all malignancies diagnosed in the United States.  

Medical journals in the past few years have estimated that approximately 57,000 new cases of thyroid cancer will be diagnosed annually in the U.S. These cases will be diagnosed three times more commonly in women than men and there will be an estimated 2,000 deaths from the disease this year. It is important to note the incidence of new cases diagnosed appears to be stabilizing. 

The commonly accepted risk factors for developing thyroid cancer are a positive family history of the disease, female gender, age over 40 years and prior history of radiation exposure. The incidence of thyroid malignancies rose dramatically in those people exposed to excessive radiation in the Chernobyl nuclear reactor disaster of 1986. 

There are four major types of thyroid cancer, with a number of subtypes based on the microscopic appearance of the tumors. The major types are: papillary, follicular, medullary and anaplastic. Papillary thyroid cancer is by far the most common, with 65-85 percent of cases diagnosed. Anaplastic is the least common, but most aggressive. The papillary and follicular cancers derive from the follicular cells that produce thyroid hormone and they maintain differentiated thyroid function. Together these two tumor types are classified as “differentiated thyroid cancers.” Anaplastic thyroid cancers, thought to be derived from the same cells, have lost their thyroid function and have been classified as poorly differentiated or undifferentiated cancers. The medullary thyroid carcinomas, making up approximately 5 percent of all thyroid cancers, arise from the parafollicular C-cells. These cells produce the hormone calcitonin, which is involved in regulating blood and bone calcium levels.  

Approximately 25 percent of medullary thyroid carcinomas are inherited, versus approximately 5 percent inheritance for papillary carcinoma. The inherited form of medullary thyroid carcinoma is a component of an autosomal dominant cancer syndrome known as multiple endocrine neoplasia type II. A number of genetic markers for thyroid cancers have been identified. This is an exciting area of active research in developing newer forms of treatment.  

Thyroid cancer can show itself in a mass in the neck with no other symptoms. There may also be neck or throat pain, voice change, hoarseness or difficulty breathing or swallowing. A lump may be noted in the neck below the area of the thyroid cartilage (Adam’s apple). This may appear more prominent when the neck is extended, and it may move up and down with swallowing. You should schedule a physician visit for further evaluation if you have a mass in your neck such as that. 

Many thyroid nodules are found during routine physical exams or with ultrasound screening exams. Once a nodule is identified, the physician will conduct a complete head and neck examination to evaluate for any lymph node enlargement or impaired vocal cord function. An ultrasound exam of the neck mass is usually carried out as well. If the nodule does involve the thyroid gland, the ultrasound can identify suspicious features. If the thyroid nodule has blurring of the margins around the nodule, an irregular shape, is solid, has internal microcalcifications, demonstrates increased blood flow in the nodule or other suspicious findings such as abnormal appearing surrounding lymph nodes, then a needle biopsy of the nodule is usually performed.  

If the biopsy is positive for thyroid cancer, the type of cancer is usually identified. It is sometimes necessary to obtain further studies on the specimen to confirm the diagnosis. Once the diagnosis is established, then the extent of the disease or stage will be determined.  

Thyroid cancer staging is done in conjunction with the type of cancer to aid in determining treatment options and to gauge prognosis. Staging can be accomplished using any number of imaging techniques, such as ultrasound, CT scanning, MRI scanning, and nuclear scanning.  

In staging thyroid cancer, the American Joint Committee on Cancer’s TNM staging system is used. The ‘T,” or tumor, indicates the size of the primary tumor and whether it has grown into nearby areas. The ‘N,’ or node, describes the extent of spread to nearby lymph nodes, and the ‘M,’ or metastasis, indicates whether cancer has spread to other parts of the body.  

The staging system for differentiated thyroid cancer then takes into consideration the T, N, and M status and the patient’s age. The stages are from I to IV-c, with the worst prognosis as the stage increases. Age does not affect staging for medullary thyroid carcinoma and all anaplastic thyroid carcinomas are considered to be in the advanced stage (IV-a, IV-b, IV-c).  

For most thyroid cancers, surgery is the recommended treatment. The amount of surgery depends upon whether the disease is localized to the thyroid gland or has involved the surrounding lymph nodes or other structures in the neck or upper chest. A patient having a thyroidectomy is the most common procedure. Patients may also require radioactive iodine therapy and suppressive hormone treatment with thyroid hormone. More advanced disease may require more extensive surgery, chemotherapy, external beam irradiation, immune therapy, or a combination of treatments. The prognosis for the most common thyroid malignancies -- papillary and follicular carcinomas -- is greater than 90 percent for 10-year survival. 

It is important to identify low-risk thyroid malignancies, which studies now indicate may not need the same treatment options as more aggressive tumors. It is also equally important that more aggressive thyroid tumors be identified early and treated more aggressively. Physicians now have new ways to classify tumor risk, which will facilitate better treatment options.