The thyroid gland is located in the front of the neck at the base of the throat. Thyroid tumors are either benign (noncancerous) or malignant (cancerous) growths. Examples of benign tumors are adenomas, which may secrete thyroid hormone.
Malignant tumors are more rare and are more common in women than in men. According to the American Cancer Society (ACS), over 56,000 cases of thyroid cancer are expected to be diagnosed in the U.S. in 2012.
What are thyroid adenomas?
Thyroid adenomas are small growths (nodules) that start in the cell layer that lines the inner surface of the thyroid gland. The adenoma itself may secrete thyroid hormone.
If the adenoma secretes enough thyroid hormone, it may cause hyperthyroidism. Thyroid adenomas may be treated if they cause hyperthyroidism. Treatment may include surgery to remove part of the thyroid (the overactive nodule).
What are cancerous thyroid tumors?
Cancer of the thyroid occurs more often in people who have undergone radiation to the head, neck, or chest. However, it may occur in people without any known risk factors. Most thyroid cancer can be cured with appropriate treatment.
Thyroid cancer usually appears as nodules within the thyroid gland. Some signs that a nodule may be cancerous include:
- Presence of a single nodule rather than multiple nodules
- Thyroid scan reveals the nodule is not functioning
- Nodule is solid instead of filled with fluid (cyst)
- Nodule is hard
- Nodule grows fast
What are the symptoms of thyroid cancer?
The first sign of a cancerous nodule in the thyroid gland is usually a painless lump in the neck.
Other symptoms may include:
- Hoarseness or loss of voice as the cancer presses on the nerves to the voice box
- Difficulty swallowing as the cancer presses on the throat
- Throat or neck pain that does not go away
- Breathing problems
- A cough that does not go away
However, the symptoms of thyroid cancer may resemble other conditions or medical problems. Always consult your doctor for a diagnosis.
The types of thyroid cancer are:
Papillary carcinoma – the most common form of thyroid cancer, which accounts for 70 to 80 per cent of cases. This cancer affects the cells that produce thyroid hormone. It grows slowly.
Thyroid Tumor this cancer also affects thyroid hormone-producing cells. However, it grows more quickly. This cancer accounts for around 10 per cent of thyroid cancers.
Medullary carcinoma – this type of cancer tends to run in families. The symptoms may mimic those of Cushing’s syndrome. It does not involve thyroid hormone-producing cells and accounts for 5 to 10 per cent of thyroid cancers.
Anaplastic carcinoma – this is the most aggressive and malignant form of thyroid cancer. It tends to grow rapidly and block the windpipe. It generally originates in benign or low grade cancerous thyroid tumours and accounts for around 7 per cent of thyroid cancers.
Thyroid lymphoma – this occurs when white blood cells (lymphocytes) invade the thyroid and become cancerous. This accounts for around 4 per cent of thyroid cancers.
Anyone can develop thyroid cancer, regardless of age or gender. Some of the risk factors associated with thyroid cancer include:
- Radiation exposure – high doses of radiation were used during the 1950s to treat disorders of the throat and skin. Absorbed radioactive fallout following nuclear accidents is also a risk factor.
- Chronic goitre –persistent enlargement of the thyroid gland.
- Family history – a susceptibility can be inherited.
- Gender – more women than men develop thyroid cancer.
Diagnosing thyroid cancer involves a number of tests, including:
- Physical examination
- Blood tests
- Ultrasound scans
- Examination of the vocal cords
- Tissue biopsy
Treatment depends on the type, size and stage of the cancer, and the patient’s age and health. Options may include:
Surgery – the favoured treatment for papillary, follicular and medullary cancers. The thyroid gland is removed, either whole or in part depending on the size of the cancer and how much of the gland is affected. Nearby lymph nodes may also be removed.
Radiation therapy – Radioactive iodine is used to kill any remaining thyroid hormone-producing cells. This normally requires the patient to stop thyroxine treatment for a few weeks to cause thyroid stimulating hormone (TSH) levels to rise and thereby stimulate the thyroid cells to absorb the radioactive iodine. Patients can become significantly hypothyroid during this period.
External radiation is frequently used for medullary and anaplastic cancer, and for tumours which do not respond to radioactive iodine.
Hormone therapy -patients require thyroid hormone replacement in the form of thyroxine following surgery.
The doses given are generally higher than for other hypothyroid patients, in order to suppress the production of thyroid stimulating hormone and thereby suppress the growth of thyroid cells.
Chemotherapy – drugs that kill cancer cells are used for the cancers that do not involve the thyroid hormone-producing cells.