The thyroid gland is situated in the front portion of the neck and performs the function of producing the thyroid hormone which regulates the metabolism in the body. The thyroid gland is shaped like a butterfly and has two lobes, the right and the left which are joined by a fibrous bridge which is known as the isthmus. Cells known as the parafollicular cells present in the thyroid gland are responsible for producing the thyroid hormone. Excessive production of thyroid hormone results in hyperthyroidism which can cause sweating, weight loss, rapid heartbeats, anxiety and palpitations. Little production of the hormone known as hypothyroidism can result in thinning of hair, weight gain, lethargy, cold intolerance etc. Thyroid stimulating hormone which is secreted by the pituitary gland located in the brain regulates the amount of thyroid hormone in the body. Other cells present in the thyroid gland like C cells regulate the number of calcium levels in the body, lymphocytes are a part of the immune system of the body and stromal cells help the structure of the thyroid gland.
Thyroid cancer arises from the tissues present in the thyroid gland. There is abnormal growth of the cells which might spread to other parts of the body as well. If cancer occurs due to spread from other locations, it is not classified as thyroid cancer. Thyroid cancer occurs when there is change or genetic mutation in the cells. The number of abnormal cells multiplies in the thyroid and on reaching a large quantity, these cells form a tumour. In case thyroid cancer is diagnosed early, it is one of the most easily treatable types of cancer.
Thyroid cancer is one of the most common types of endocrine cancer. Cancer differs from goitre in which there is an enlargement of the thyroid gland which happens because of hyper or hypothyroidism. Goitre is caused mainly due to deficiency of iodine in the body. Graves’ disease can also be associated with enlargement of the thyroid gland. In areas where iodinated table salt is used, Hashimoto’s thyroiditis an autoimmune disease is the most common cause of goitre.
It is believed that around 3.2 million people suffer from thyroid cancer globally. This disease generally occurs between the age of 35 and 65 years. Women are more prone to get affected than men. Asian origin people are more likely to develop this disease. While the number of cases of thyroid cancer has increased in the last 30 years, the rate of death has not changed. This suggests that medical care professionals and doctors have become better at detecting lumps in thyroid glands and making a proper diagnosis.
The different classifications of thyroid cancer include:
- Papillary thyroid carcinoma: This type is the most commonly found type of thyroid cancer. It occurs in almost 75-85% of the cases. Often found in young females, this type has a good prognosis. It grows slowly but might spread to the lymph nodes in the neck.
- Follicular thyroid carcinoma: It is the next most common type of thyroid cancer. It is found in almost 10-20% of the cases. It might occur in people with Cowden syndrome.
- Medullary thyroid carcinoma: This makes up about 5-8% of the cases. This type is associated with problems in other glands and is likely to run in the family. This type is generally detected early on in blood tests because of the production of a hormone known as calcitonin.
- Anaplastic thyroid cancer: This is the most severe type of thyroid cancer as it is very advanced. This is a very rare form of thyroid cancer and is hard to treat.
Thyroid cancer occurs in women more than men. Women generally develop thyroid cancer in their 40’s and 50’s while men tend to get it between the ages of 60-70 years. Some kinds of inherited genetic syndromes like multiple endocrine neoplasias and familial medullary thyroid cancer increase the risk of thyroid cancer. People with low intake of iodine in their diets are more prone to thyroid cancer. There can also be a relationship between not well-controlled diabetes and increased risk of thyroid cancer.
Thyroid cancer is mostly detected when the individual or the doctor feels a lump in the area where the thyroid gland is located in the lower front of the neck. It is mostly found incidentally and is painless. Most of the people have a normal functioning thyroid gland when a tumour is detected and have no signs of hyper or hypothyroidism. In case the tumour is large, it might cause signs such as difficulty in swallowing food which is rare. In case the recurrent laryngeal nerve is involved, hoarseness might be experienced.
There are very few symptoms at the beginning of the disease. As a tumour grows in size, other symptoms like pain in the neck and throat, lumps in the neck, cough, difficulty in swallowing, swollen lymph nodes and enlarged thyroid gland, vocal changes like hoarseness might be experienced. A tumour may compress the oesophagus that may cause a problem in the vocal chords. But the chances of such a thing happening are very low. Thyroid cancer can spread to the local lymph nodes and further.
There is no clear cause for the occurrence of thyroid cancer, though there are some factors that are associated with a greater risk of developing thyroid cancer. Patients without exposure to any risk factor can also develop thyroid cancer. Some causes are:
- Iodine deficiency: If inadequate amounts of iodine intake are there in the diet, the individual has a risk of developing thyroid cancer. But this rare as iodine is normally added to salt and other foods.
- Inherited genetic syndromes: This is mostly a genetic disease which is inherited from the parents. In most of the cases of medullary thyroid cancer, a genetic factor is present. It is most often due to the inheritance of an abnormal gene. The mutations in the cells make the cells to grow and multiply. This accumulation of cells results in the formation of a tumour.
- Radiation Exposure: In case there has been too much radiation exposure as a child, an example too many x-rays, there is a higher chance of getting thyroid cancer.
The doctor will identify thyroid cancer symptoms during physical examinations. They will then refer the patient to a thyroidologist or an endocrinologist. The diagnosis of thyroid cancer begins before the development of symptoms. A lump in the thyroid gland can be discovered during the routine physical examination of the neck by the doctors or even by the patients themselves. Once a lump is found in the thyroid gland, it is important to find out if the lump is malignant or benign. An ultrasound will be performed to find out if there are multiple nodules or just a single nodule present. Ultrasound also helps in determining if the lump is filled with fluid or if it is solid. Ultrasound can also help the doctor in determining the appearance of the thyroid gland and look for any irregularities and inflammation and also for the presence of enlarged nymph nodes nearby which might indicate metastatic cancer.
The next step performed by the doctor usually is a fine needle aspiration biopsy (FNAB). Fine needle aspiration biopsy is a procedure performed to obtain samples of the cells from the nodule in the thyroid gland to determine if it is malignant or cancerous. A thin needle is put into the nodule using an ultrasound to obtain cells from the nodules. These cells are then examined by a pathologist to find out if the nodule is cancerous. If the cells are cancerous then the pathologist will also find out what type of cancer it is. In some cases, the results of the biopsy may be uncertain or unclear, to clear out any doubt the biopsy will be conducted again to get a more cell and a better sample to study on.
Radio-iodine testing can also be done if the results from the fine needle aspiration biopsy are still unclear or indefinite. The patient will be given some radioactive iodine to swallow which will be then taken up by the thyroid gland. The gland will then be scanned using a Geiger counter-type apparatus to check how much radioactive iodine did the thyroid gland take up. If the thyroid gland nodules take up a lot of radioactive iodine it will be classified as a “hot nodule”. There are very rare cases of hot nodules being cancerous. The thyroid gland nodules that take up no radioactive iodine or very little radioactive iodine are classified as “cold nodules”. Although most cold nodules are not cancerous and only 5% of the cold nodules turn out to be malignant. Thyroid scans and tests can be helpful but they are not the first-line tests and fine needle aspiration biopsy is a much better and useful test for the thyroid gland. Blood tests may also be conducted to know the function of the thyroid gland. Measuring the levels of blood in thyroid stimulating hormone (TSH) can be useful in determining the functions of the thyroid. Calcitonin levels increase in medullary thyroid cancer. But medullary thyroid cancer is a very rare type and a test is usually not recommended for screening for cancer.
MTC, MEN and FMTC are hereditary in nature. Genetic tests of family members may also be done. Test for other types of tumours such as pheochromocytoma may also be done.
There are many ways to treat a thyroid cancer. The choice of treatment depends on the type and stage of the thyroid cancer. It also depends on the age and health of the patient. The options available for the treatment are as follows:
- Lobectomy: There are two lobes in the thyroid which are joined by the isthmus which is a fibrous tissue bridge. If the cancerous tumours affect only a confined area, the doctors will remove the affected lobe.
Lymph nodes removal: During the surgery, the doctors may notice the spread of thyroid cancer to the local lymph nodes. These nodes will be removed by the doctors. Thyroid cancer can spread further from the local lymph nodes.
- Open biopsy: In some cases, the cancerous nature of the thyroid gland nodule is still unclear, even after conducting the fine needle aspiration. In that cases, the surgeon will remove the nodule and send all the tissues forward to be evaluated by a pathologist for further diagnosis.
- Total Thyroidectomy: In this procedure, all parts of the thyroid gland of the patient are removed. This is the most common type of surgery conducted in the case of thyroid cancer.
- Chemotherapy: Chemotherapy is rarely required for any type of thyroid cancer. Chemotherapy may be used in some situations where the thyroid cancer does not react to other forms of treatment.
Radiotherapy: If the thyroid nodules don’t take up any radioactive iodine, radiation therapy might be required. Radioactive iodine tests are done before considering for radiation therapy. Radiations are used to remove the lumps or tumours in this type of surgery.
- Targeted therapy: A new form of treatment that only targets certain parts of cancerous cells. It slows or stops the growth of these cells. This procedure is usually done in forms of pills. There are fewer side effects from this therapy than from chemotherapy.
Thyroid cancer can recur in the lymph nodes in the neck even after the surgery is done. Thyroid cancer can also recur in the small pieces of tissues that may be left behind during the surgery. It also may recur in the other parts of the body. Thyroid cancer can spread through the lobes to the lymph nodes and then further. Radiation treatments to the neck and the head of the patient may also worsen cancer if not done correctly. Thyroid cancer may also result in difficulty in swallowing the food. A tumour may compress the oesophagus that may cause a problem in the vocal chords. But the chances of such a thing happening are very low.
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