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Thyroid Cancer: Symptoms, Diagnosis and Treatment

Thyroid cancer is a rare type of cancer, representing only about 1 percent of all cancer cases. This type of cancer is about three times as prevalent in women as it is in men.

The thyroid gland is an organ that produces hormones that regulate multiple functions inside the body including heart rate, blood pressure, temperature and body weight. Thyroid cancer, however, doesn't usually alter thyroid function.

Types of Thyroid Cancer

Diagnosing thyroid cancer consists of inspecting a sample (biopsy) of the cancerous cells and classifying it as one of four types:

anaplastic
follicular
medullary
papillary.

More than 90 percent of all thyroid cancers fall into either the papillary or follicular categories. Papillary thyroid cancer is the most common and least aggressive form of thyroid cancer and is slow to metastasize. Follicular thyroid cancer is the second most common form and is more likely to both metastasize and recur following treatment.

Medullary thyroid cancer is linked to heredity, with 25 percent of cases running in families. Anaplastic thyroid cancer is the rarest and most aggressive form of thyroid cancer and can develop from the papillary and follicular forms through unknown pathways.

Risk Factors for Thyroid Cancer

Risk factors for thyroid cancer include:

age between 25 and 65
a history of goiter (enlarged thyroid)
Asian descent
family members with thyroid disease, Cowden's disease or Gardner's syndrome
female gender
radiation treatments to the head or neck, especially during infancy or childhood.

Of all the symptoms, the most significant are swelling of the neck, new or enlarged nodules on the thyroid, changes in voice quality and hoarseness, especially when those symptoms occur in patients with one or more of the risk factors noted above.

The risk factor that may point most strongly toward cancer is the exposure of the neck to radiation, especially during childhood. Such exposure makes it much more likely that nodules are cancerous.

Thyroid Cancer Symptoms

Symptoms of thyroid cancer include:

a nodule (raised bump) on the thyroid
changes in voice quality
diarrhea (specific to medullary thyroid cancer)
difficulty swallowing
enlarged thyroid gland
hoarseness
persistent cough, especially with bleeding
swollen neck.

Diagnosis of Thyroid Cancer

The first diagnostic tool used in cases of suspected thyroid cancer is fine needle aspiration cytology (also called needle aspiration biopsy), in which a small sample of a suspicious nodule is removed for examination.

Larger samples can be obtained using a mini trucut biopsy. A biopsy is an essential part of the diagnosis of thyroid cancer, as it is otherwise impossible to differentiate between a benign and a malignant nodule.

Since the majority of thyroid cancer patients have normal thyroid function, tests to determine the status of the thyroid do not contribute much information to the diagnosis. Blood tests for calcitonin and thyroglobulin, however, can help determine if thyroid cancer is present. Elevated levels of calcitonin may indicate medulliary thyroid cancer, while elevated levels of thyroglobulin may indicate papillary or follicular thyroid cancer.

Once a lesion has been determined to be malignant, further investigation can be done using ultrasound. This is a safe and noninvasive way of determining the size and extent of any nodules, as well as surrounding tissue involvement.

In cases where the original tumor has metastasized and spread, computerized tomography (CT) scans or magnetic resonance imaging (MRI) can be used to help determine the degree to which metastasis has occurred.

Thyroid Cancer Treatments

There is debate in medicine about how best to treat thyroid cancer. This debate is fueled by a lack of randomized trials. Much of the investigation on treatment that has been done has taken the form of retrospective studies, where researchers review the treatments and outcomes of past cases.

The prognosis for the main types of thyroid cancer is relatively good, with one study putting 40-year survival rates at 94 percent for patients with follicular cancer and 84 percent for patients with papillary cancer. Even in cases of metastatic tumors, long-term survival rates for papillary and follicular cancer are generally good.

Anaplastic thyroid cancer, though much less prevalent, has a far worse prognosis, with survival measured in months. Death is often from suffocation as a result of rapid tumor growth and distant spread of metastases.

Here are the treatment options for each type of thyroid cancer:

Treatment of Anaplastic Thyroid Cancer: Due to the anaplastic thyroid cancer's tendency to spread rapidly through surrounding tissues, neither surgery nor any other treatments are likely to cure it. Palliation (relieving symptoms but not curing the disease) is the primary treatment available for this form of thyroid cancer, usually in the form of a combination of chemotherapy and radiation therapy.
Treatment of Medullary Thyroid Cancer: Surgical treatment is similar to that for papillary and follicular thyroid cancer (see below). Following surgical treatment, external beam radiotherapy is used to help reduce the risk of recurrence.
Treatment of Papillary and Follicular Thyroid Cancer: Depending on the degree of thyroid involvement, surgical treatment may include either hemithyroidectomy (partial removal of the thyroid) or total thyroidectomy. Surgical treatment is usually followed by radioiodine therapy, which helps clear any remaining cancerous lesions, both in the thyroid and at any metastatic sites.

Resources

National Cancer Institute. (n.d.). Thyroid Cancer. Retrieved June 20, 2007, from http://www.cancer.gov/cancertopics/types/thyroid/.

National Institutes of Health. (2007). MedlinePlus Medical Encyclopedia: Thyroid cancer. Retrieved June 20, 2007 from http://www.nlm.nih.gov/medlineplus/ency/article/001213.htm.

Nix, P., Nicolaides, A., & Coatesworth, A. P. (2005). Thyroid cancer review 1: Presentation and investigation of thyroid cancer. International Journal of Clinical Practice, 59(11), 1340-1344.

Nix, P., Nicolaides, A., & Coatesworth, A. P. (2005). Thyroid cancer review 2: Management of differentiated thyroid cancers. International Journal of Clinical Practice, 59(12), 1459-1463.

Wiseman, S., Loree, T., Rigual, N., Hicks, W., Douglas, W., Anderson, G., & Stoler, D. (2003). Anaplastic transformation of thyroid cancer: Review of clinical, pathologic, and molecular evidence provides new insights into disease biology and future therapy. Head & Neck, 25, 662-670.

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