Thyroid Cancer

What is thyroid cancer?

Certain factors may increase the risk of developing thyroid cancer.

 

• Thyroid cancer occurs more often in people between the ages of 25 and 65 years.
• People who have been exposed to radiation or received radiation treatments to the head and neck during infancy or childhood have a greater chance of developing thyroid cancer. The cancer may appear as early as 5 years after exposure or may occur 20 or more years later.
• People who have had goiter (enlarged thyroid) or a family history of thyroid disease have an increased risk of developing thyroid cancer.
• Thyroid cancer is more common in women than in men.
• Asian people have an increased risk of developing thyroid cancer.

 

A doctor should be seen if there is a lump or swelling in the front of the neck or in other parts of the neck.

If there are symptoms, a doctor will feel the patient’s thyroid and check for lumps in the neck. The doctor may order blood tests and special scans of the neck. If there is a lump present in the thyroid the doctor may take a small amount of tissue from the thyroid by the use of a small needle. The tissue is then looked at under a microscope to see whether it contains cancer cells.(see article on thyroid nodules).

There are four main types of thyroid cancer ( based on how the cancer cells look under the microscope.)

Papillary Cancer:

Papillary tumors are the most common of all thyroid cancers (>70%). This tumor arises as an irregular, solid or cystic mass that arises from otherwise normal thyroid tissue. This cancer has a high cure rate with ten year survival rates for all patients with papillary thyroid cancer estimated at 80-90%. Cervical metastasis (spread to lymph nodes in the neck ) are present in 50% of small tumors and in over 75% of the larger thyroid cancers. The presence of lymph node metastasis in these cervical areas causes a higher recurrence rate but not a higher mortality rate. Distant metastasis (spread) is uncommon, but lung and bone are the most common sites. Tumors that invade or extend beyond the thyroid capsule have a worsened prognosis because of a high local recurrence rate.

Characteristics of Papillary Thyroid Cancer

• Peak onset ages 30 through 50
• Female more common than males 3 to 1 ratio
• Prognosis directly related to size (less the 1.5cm (1/2 inch) good
• prognosis
• Account for 85% of thyroid cancers due to radiation exposure
• Spread to lymph nodes of the neck present in more than 50% of
• cases.
• Distant spread (to lung and bones) is very uncommon
• Overall cure rate very high (near 100% for small lesions in young patients.

2. Follicular Cancer: ( or Hurthle cell)

Follicular carcinomas are the second most common thyroid cancers (15%). Follicular carcinoma is considered more malignant (aggressive) than papillary carcinoma. It occurs in a slightly older age group than papillary and is also less common in children. In contrast to papillary cancer, it occurs rarely after radiation therapy. Mortality is related to the degree of vascular invasion. Age is a very important factor in terms of prognosis. Patients over 40 have a more aggressive disease and typically the tumor does not concentrate iodine as well as in younger patients. Vascular invasion is characteristic for follicular carcinoma and therefore distant metastasis is more common. Distant metastasis may occur in a small primary. Lung, bone, brain liver, bladder, and skin are potential sites of distant spread. Lymph node involvement is far less common than in papillary carcinoma (8-13%).

Characteristics of Follicular Thyroid Cancer

• Peak onset ages 40 through 60
• Females more common than males by 3 to 1 ratio
• Prognosis directly related to size ( less than 1cm (3/8 inch)good prognosis.
• Spread to lymph nodes is uncommon (10%)
• Invasion into vascular structures (veins and arteries) within the thyroid gland is common
• Distant spread (to lungs or bones) is uncommon, but more common than with papillary cancer.
• Overall cure rate high (near 95% for small lesions in young patients), decreases with advanced age.

Medullary Cancer:

Medullary tumors are the third most common of all thyroid cancers(5-8%)

Unlike papillary and follicular thyroid cancers which arise from thyroid hormone producing cells, medullary cancer of the thyroid originates from the parafollicular cells ( also called C cells) of the thyroid. These C cells make a different hormone called calcitonin which has nothing to do with the control of metabolism the way thyroid hormone does. This cancer has a much lower cure rate than does the “ well differentiated” thyroid cancers (papillary and follicular), but cure rates are higher than they are for anaplastic thyroid cancer. Overall 10 year survival rates are 90% when all disease is confined to the thyroid gland, 70% with spread to cervical lymph nodes, and 20% when spread to distant sites is present.

Characteristics of Medullary Cancer Thyroid Cancer

• Occurs in alone or can occur with other endocrine disorders(pheochromocytoma, hyperparathyroidism).
• Females more common than males
• Regional metastases (spread to neck lymph nodes) occurs early in the course of the disease.
• Spread to distant organs (metastasis) occurs late and can be to the liver, bone, brain, and adrenal medulla.
• Not associated with radiation exposure
• Usually originates in the upper central lobe of the thyroid
• Poor prognostic factors include age >50, male, distant spread,And MEN II B
• Residual disease (following surgery) or recurrence can be detectedby measuring calcitonin.

Anaplastic Cancer:

Anaplastic tumors are the least common (about 2-3%) and the most deadly of all thyroid cancers. This cancer has a very low cure rate of only 10% of patients alive 3 years after it is diagnosed. Like papillary cancer, anaplastic cancer may arise many years following radiation exposure. Cervical metastasis (spread to lymph nodes in the neck) are present in the vast majority of cases at the time of diagnosis. The presence of lymph node metastasis in these cervical areas causes a higher recurrence rate and is predictive of a high mortality rate. The most common way this cancer becomes evident is by the patient or family member noticing a growing neck mass. This tumor invade adjacent structures and metastasize extensively to cervical lymph nodes and distant organs such as lung and bone. Most of these cancers are so aggressively attached to vital structures that they are inoperable at the time of diagnosis.

Characteristics of Anaplastic Thyroid Cancer

• Peak onset age 65 and older
• Very rare in young patients
• Males more common than females by 2 to 1 ratio
• Typically presents as rapidly growing neck mass
• Can occur many years after radiation exposure
• Spread to lymph nodes of the neck present in more than 90% of cases.
• Distant spread (to lungs or bones) is very common even when first diagnosed.
• Overall cure rate very low

 

Treatment of Thyroid Cancer

The type of treatment used in thyroid cancer often depends on the type of tumor present. There are three main treatment modalities used with thyroid cancer.

• Surgical excision of the tumor
• Radiation
• Thyroid medication

Surgical treatment is usually either a thyroid lobectomy with isthmusthectomy or a total thyroidectomy.

Lobectomy with Isthmusthectomy: This simple means removal of a thyroid lobe and the isthmus (the part that connects the two lobes).

Total Thyroidectomy: This operation is designed to remove all the thyroid tissue.

Complications from Surgery:

• Injury to recurrent laryngeal nerve: This would cause permanent hoarseness of the voice.
• Low Calcium: This would occur if the parathyroid glands by the thyroid gland where injured with surgery. It would only occur with the total thyroidectomy surgery and not with a simple lobectomy.

Papillary Cancer

Surgery:

There is some controversy in dealing with small papillary cancers.

Papillary carcinomas that are well circumscribed, isolated, and less than 1cm in a young patient (20-40) without a history of radiation exposure may be treated with thyroid lobectomy and isthmusthectomy. All others should probably be treated with total thyroidectomy and removal of any enlarged lymph nodes in the central or lateral neck areas.

Radiation:

Thyroid cells are unique in that they have the cellular mechanism to absorb iodine. The iodine is used by thyroid cells to make thyroid hormone. No other cell in the body can absorb or concentrate iodine. Physicians can take advantage of this fact and give radioactive iodine to patients with thyroid cancer. There are several types of radioactive iodine, with one type being toxic to cells. Papillary cancer cells absorb iodine and therefore they can be targeted for death by giving the toxic isotope (I-131). Once again, not everybody with papillary thyroid cancer needs this therapy, but those with larger tumors, spread to lymph nodes or other areas, tumors which appear aggressive microscopically, and older patients may benefit from this therapy. This treatment is given only after a total thyroidectomy surgery.

Thyroid Hormone Pills:

Regardless of whether a patient has just one thyroid lobe and the isthmus removed, or the entire thyroid gland removed, most experts agree they should be placed on thyroid hormone for the rest of their lives. This is to replace the hormone in those who have no thyroid left, and to suppress further growth of the gland in those with some tissue left in the neck. There is good evidence that papillary carcinoma responds to thyroid stimulating hormone (TSH) secreted by the pituitary, therefore, exogenous thyroid hormone is given which results in decreased TSH levels and a lower impetus for any remaining cancer cells to grow. Recurrence and mortality rates have been shown to be lower in patients receiving suppression.

Follicular Cancer

Surgery:

There is some controversy in treatment of small follicular thyroid cancers. Some surgeons feel that well circumscribed, isolated, minimally invasive, and less than 1cm in size tumors in young patients (<40) may be treated with thyroid lobectomy and isthmusthectomy. All others should probably be treated with total thyroidectomy and removal of any enlarged lymph nodes in the central or lateral neck areas.

Radiation:

Similar to papillary thyroid cancer, follicular cancer can be treated with radioactive iodine treatments. Follicular cancer cells absorb iodine (although to a lesser degree in older patients) and therefore they can be targeted for death by giving the toxic isotope ( I-131 ). Once again, not everybody with follicular thyroid cancer needs this therapy, but those with larger tumors, spread to lymph nodes or other areas, tumors which appear aggressive microscopically, tumors which invade blood vessels within the thyroid, and older patients may benefit from this therapy. Once again this treatment is given only after a total thyroidectomy surgery.

Thyroid Hormone Pills:

Regardless of whether a patient has just one thyroid lobe and the isthmus removed, or the entire thyroid gland removed, most experts agree they should be placed on thyroid hormone for the rest of their lives. This is to replace the hormone in those who have no thyroid left, and to suppress further growth of the gland in those with some tissue left in the neck. There is good evidence that follicular carcinoma (like papillary cancer) responds to thyroid stimulating hormone (TSH) secreted by pituitary, therefore, exogenous thyroid hormone is given which results in decreased TSH levels and a lower impetus for and remaining cancer cells to grow. Recurrence and mortality rates have been shown to be lower in patients receiving suppression.

Medullary Cancer

Surgery:

In contrast to papillary and follicular cancers, little controversy exists when discussing the management of medullary thyroid cancer. After assessment and treatment of associated endocrine conditions (such as pheochromocytomas if present) all patients should receive total thyroidectomy, a complete central neck dissection (removal of all lymph nodes and fatty tissues in the central area of the neck), and removal of all lymph nodes and surrounding fatty tissues within the side of the neck which harbored the tumor.

Radiation:

Although thyroid cells have the cellular mechanism to absorb iodine (see above concerning papillary caner), medullary thyroid cancer does not arise from this type of thyroid cell. Therefore, radioactive iodine therapy is not useful for the treatment of medullary thyroid cancer. Similarly if medullary cancer spreads to distant sites, it cannot be found by iodine scanning the way that distant spread from papillary or follicular cancer can.

Thyroid Hormone Pills:

Thyroid hormone replacement medication should be given because of the total thyroidectomy surgery. Medullary cancer does respond to thyroid stimulating hormone (TSH) secreted by the pituitary and thus exogenous thyroid hormone does not help to decrease the recurrence rate or improve the mortality rates as it does with papillary and follicular cancer.

Anaplastic Thyroid Cancer

Management:

The major problem with anaplastic thyroid cancer is that it is usually too aggressive and invasive when it is diagnosed. Therefore, only a small portion of patients can undergo surgical resection of the cancer in hopes of cure. For those patients who are diagnosed at an earlier stage, total thyroidectomy is necessary. Many patients, especially those who have advanced cancer and cannot undergo surgical resection, will benefit from external-beam radiation (this is different from radioactive iodine). Some chemotherapy treatments may also be beneficial to patients with anaplastic thyroid cancer.

Long Term Follow Up:

The usual follow up is at 1,3,6,12months and then yearly. A physical examination to see if there is any sign of recurrent disease in the neck would be done. Yearly chest x-rays, TSH levels, and thyroglobulin levels are also usually followed. Thyroglobulin is not useful as a screening test for the initial diagnosis of thyroid cancer but it is quite useful in follow up of well differentiated carcinoma (if a total thyroidectomy has been performed). A high serum thyroglobulin level that had previously been low following total thyroidectomy may be a sign of a recurrence. Also I131 Total Body Scans may be ordered if there is any question of recurrence. In Medullary Cancer serum calcitonin levels would also be followed.