What is Thyroid Cancer ans What Causes It?
Thyroid cancer is a cancer originating from follicular or parafollicular thyroid cells.
The most effective management of aggressive thyroid cancers is surgical removal of thyroid gland (thyroidectomy) followed by radioactive iodine ablation and TSH-suppression therapy.
Chemotherapy or radiotherapy may also be used in cases of distant metastases or advanced cancer stage.
Five year survival rates are 98% in the United States.
Most often the first symptom of thyroid cancer is a nodule in the thyroid region of the neck.
However, many adults have small nodules in their thyroids, but typically under 5% of these nodules are found to be malignant.
Sometimes the first sign is an enlarged lymph node.
Later symptoms that can be present are pain in the anterior region of the neck and changes in voice due to an involvement of the recurrent laryngeal nerve.
Symptoms of hyperthyroidism or hypothyroidism may be associated with a large or metastatic well-differentiated tumor.
Thyroid nodules are of particular concern when they are found in those under the age of 20. The presentation of benign nodules at this age is less likely, and thus the potential for malignancy is far greater.
Thyroid Cancers are thought to be related to to a number of environmental and genetic predisposing factors, but significant uncertainty remains regarding its causes.
Environmental exposure to ionizing radiation from both natural background sources and artificial sources are suspected to play a significant role, and there are significant increased rates of thyroid cancer rates in those exposed to mantlefield radiation for lymphoma, and those exposed to iodine-131.
Thyroiditis and other thyroid disease also predisposes to thyroid cancer.
After a thyroid nodule is found during a physical examination, a referral to an endocrinologist, or a thyroidologist may occur. Most commonly an ultrasound is performed to confirm the presence of a nodule, and assess the status of the whole gland.
Measurement of thyroid stimulating hormone and anti-thyroid antibodies will help decide if there is a functional thyroid disease such as Hashimoto's thyroiditis present, a known cause of a benign nodular goiter.
Finally, to achieve a definitive diagnosis before deciding on treatment, a fine needle aspiration cytology test is usually performed.
Thyroid cancers can be classified according to their histopathological characteristics. The following variants can be distinguished (distribution over various subtypes may show regional variation):
Papillary thyroid cancer often in young females – excellent prognosis.
Follicular thyroid cancer - occasionally seen in patients with Cowden syndrome
Medullary thyroid cancer - cancer of the parafollicular cells, often part of multiple endocrine neoplasia type 2.
Poorly differentiated thyroid cancer
Anaplastic thyroid cancer - It is not responsive to treatment and can cause pressure symptoms.
Squamous cell thyroid carcinoma
Sarcoma of thyroid
The follicular and papillary types together can be classified as "differentiated thyroid cancer".
These types have a more favorable prognosis than the medullary and undifferentiated types.
Detection of any metastases of thyroid cancer can be performed with a full body scintigraphy using iodine-131.
Thyroidectomy and dissection of central neck compartment is initial step in treatment of thyroid cancer in majority of cases.
The prognosis of thyroid cancer is related to the type of cancer and the stage at the time of diagnosis.
For the most common form of thyroid cancer, papillary, the overall prognosis is excellent.
The increased incidence of papillary thyroid carcinoma in recent years is likely related to increased and earlier diagnosis.
One can look at the trend to earlier diagnosis in two ways.
The first is that many of these cancers are small and not likely to develop into aggressive malignancies.
A second perspective is that earlier diagnosis removes these cancers at a time when they are not likely to have spread beyond the thyroid gland, thereby improving the long-term outcome for the patient.
Fortunately for those with metastatic thyroid cancer, the last 5 years has brought about a renaissance in thyroid cancer treatment.
The identification of some of the molecular or DNA abnormalities for thyroid cancer has led to the development of therapies that target these molecular defects.
More compounds are under investigation and are likely to make it through the approval process.
For differentiated thyroid carcinoma, strategies are evolving to use selected types of targeted therapy to increase radioactive iodine uptake in papillary thyroid carcinomas that have lost the ability to concentrate iodide.
This strategy would make it possible to use radioactive iodine therapy to treat "resistant" thyroid cancers. Other targeted therapies are being evaluated, making it possible that life will be extended over the next 5–10 years for those with stage III and IV thyroid cancer.
Prognosis is better in younger people than older ones.
Prognosis depends mainly on the type of cancer and cancer stage.