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WHAT IS A THYROID?

The thyroid is a small endocrine gland located in the front base of your neck, below the Adam's apple. A butterfly-shaped gland has two parts, one on either side of the windpipe and a bridge connecting the two halves, called the isthmus.

The thyroid's small size does not indicate its role in our health: it produces two hormones, thyroxine (T4) and triiodothyronine (T3), which are critical for the normal functioning of all the cells in your body. The thyroid is a part of the body's endocrine system, which regulates the functions of thyroid hormones to maintain metabolism. Thyroid hormones also regulate some essential processes in our body: body temperature, blood pressure, heart rate, calorie burning, the passage of food through the gut, muscle contraction, and replacing dying cells.

TYPES OF THYROID CANCER

As with all cancers, thyroid cancer occurs when cells in the gland multiply out of control leading to a tumor. A tumor is excessive cell growth and can be benign (non-cancerous) or malignant (cancerous).

Thyroid cancer is classified into five kinds depending on the category of cancerous cells. The thyroid gland has two types of cells: follicular and C-cells. Follicular cells produce thyroid hormones, and C-cells manufacture calcitonin, which metabolizes calcium in the body.

1. Papillary Thyroid Cancer (PTC):This type of cancer begins in the thyroid's follicular cells and typically shows a slow growth rate. PTC is the most prevalent thyroid cancer - nearly 80 per cent of thyroid cancer cases are of this type. It is usually found in one of the thyroid halves, and when you examine the tumor tissue, it appears like normal thyroid tissue. This cancer can spread to lymph nodes in the neck, but early detection can help achieve a high cure rate.
2. Follicular Thyroid Cancer (FTC): This type of cancer also begins in the follicular cells and shows a slow growth rate. It also exhibits the same normal appearance of tumor cells as in Papillary thyroid cancer but is less common and is less likely to spread to the lymph nodes though it may spread to areas outside the thyroid such as bones or lungs. It is highly curable when detected early.
   Follicular and papillary thyroid cancers comprise the majority of thyroid cancer cases.
3. Hurthle cell cancer or carcinoma: A follicular thyroid cancer is infrequent and occurs in less than 3 per cent of people. This form of cancer can affect the lymph nodes.
4. Medullary thyroid cancer (MTC) begins in the C-cells and is more aggressive than the above thyroid cancers and, therefore, more likely to attack the lymph nodes. Due to the cancerous nature of the C-cells, they release more calcitonin which can be used to detect MTC during diagnosis. The cancerous tissue is dissimilar to the normal thyroid tissue, unlike in Follicular and Papillary cancers, and early detection has a high rate of positive outcomes.
5. Anaplastic thyroid cancer. Fast-growing and the most aggressive cancer is the least common type that begins in the thyroid gland's follicular cells. Its speed of growth means it is not detected until it suddenly manifests as a lump inside the throat or affects the voice. This form of cancer also invariably spreads to the lymph nodes.

CAUSES & RISK FACTORS

The cause of thyroid cancer is still largely unknown; it is still unclear what causes changes in the thyroid cells' DNA which makes them mutate.

However, some of the more known causes are:

Age: More women than men are vulnerable to thyroid cancer, and the chances are higher during their fertility years. Research continues to explore this connection, and pregnancy, oral contraceptives, hormone replacement therapy (HRT), puberty and menopause are being researched to find the correlates.

In men, thyroid cancer can develop in their old age, potentially after age 80.

Thyroid conditions: Non-cancerous thyroid diseases such as an enlarged thyroid (also called goitre), Hashimoto's disease, a condition where your body's immune system attacks the thyroid, and nodules or tissue growths in the thyroid can be triggers for cancer. However, this does not mean every lump in the thyroid is cancerous, and only about 5 per cent of such growths turn malignant.

Obesity: It's a long-held fact that obesity is a risk factor for cancer. Though the specific link between the two is still under scrutiny, excessive fat in the body means many vital body organs are enveloped by fat cells, which cause inflammation, impact body processes, and affect the production of hormones like insulin and estrogen. It has a cumulative effect on natural cell division, leading to uncontrollable cell multiplication and creating tumors.

Family history (of thyroid cancer): Your risk increases if a family member has thyroid cancer.

WHAT ARE THE SYMPTOMS OF THYROID CANCER?

The early stages of thyroid cancer present few or no symptoms. But as the disease progress, it signals changes which you must be alert to

Lump in the neck: A hard, lump-like formation in the neck area is a probable sign of thyroid cancer. However, not all such lumps are cancerous, and the doctor will determine the nature of the growth through a biopsy.

Swollen Nodes: If your lymph nodes are continually swollen, and there is no palpable pain or swelling in the ear, nose, or throat region, it could indicate thyroid cancer.

Neck Pain: A persistent sensation of pain in the neck. Even if there is no lump or swelling, pain in the neck that travels to the ears needs to be checked out.

Difficulty in swallowing: When you experience discomfort or pain while swallowing consistently, the condition is called Dysphagia, which can be due to thyroid cancer.

Wheezing and difficulty in breathing: The location of thyroid tumors can vary, and they can grow near the windpipe, leading to breathing problems and wheezing. If you experience prolonged bouts of this condition, seek a diagnosis immediately.

Voice Change: Has your voice turned hoarse suddenly? When a tumor develops in the thyroid, it can put pressure on the voice box, which leads to a change in the tone of your voice. If you experience such changes, please seek an immediate diagnosis.

Recurring Cough: Thyroid cancer can induce persistent cough and can be wrongly attributed to respiratory issues. But if the cough continues without other flu or lung infection symptoms, it could be due to a malignant tumor.

Infectious triggers: Scientists suggest a link between specific viruses and thyroid cancer, such as the Epstein-Barr, Human Herpes Simplex = (HSV) and Hepatitis C viruses, but there is no definitive conclusion.

Hyperthyroidism: Studies point to a link between hyperthyroidism due to Graves' disease and thyroid cancer. Graves' disease causes an overproduction of thyroid hormones (hyperthyroidism). Doctors advise patients with Graves' disease to get screened for cancer regularly.

STAGES OF THYROID CANCER

Just like all cancers, thyroid cancer also has stages of development.

Doctors use a TNM system to chart the course of pancreatic cancer. It considers the following factors:

• How large is the tumor (T)?
• Has it spread outside the pancreas affecting the nearby lymph nodes (N)?
• Has it metastasized (spread to other body parts) (M)?

Thyroid Cancer has a four-stage system from Stage I to Stage IV. Staging is a way to determine the precise location of the cancerous tumor, its size and spread, and it helps them calculate its severity and the best course of treatment.

In Thyroid Cancer, the Papillary or Follicular Thyroid Cancer types are staged in two categories.

1) Papillary or Follicular Thyroid Cancer in patients under the age of 55

Stage I: The tumor, irrespective of its size, has not spread to other body parts but is localized (adjacent lymph nodes and tissues).

Stage II: The tumor, irrespective of its size, is encroaching on other parts of the body and outlying lymph nodes.

2) Papillary or Follicular Thyroid Cancer in patients 55 years and older

Stage I: Cancer restricted to the thyroid. The tumor is 2 cm or less and not spread.

Stage II: Cancer is restricted to the thyroid, and the tumor, irrespective of size, has not spread.

Stage III: The tumor is bigger than 4 cm or has spread beyond the thyroid into soft tissues such as the voice box, windpipe or food pipe but has not reached the lymph nodes. Or it is small but has affected nearby lymph nodes in the neck but not beyond. Stage IV is divided into groups A, B, and C.

Stage IVA: Cancer has spread into surrounding areas, such as bones, blood vessels, and lymph nodes but not to other organs.

Stage IVB: The tumor has affected other body parts, such as the lungs, spine or large blood vessels.

Stage IVC: The cancer is widespread in the body and has moved to organs away from the thyroid.

3) Medullary Thyroid Cancer

This type of thyroid cancer has four stages irrespective of age:

Stage I: The tumor is small and localized in the thyroid.

Stage II: Bigger than 2cms and localized in the thyroid. Or, no matter its size, it has spread to tissues outside the thyroid but not reached the lymph nodes.

Stage III: 2cms or more, cancer has spread to nearby lymph nodes and perhaps to surrounding tissues.

Stage IV: Cancer has spread to other areas in your body.

4) Anaplastic Thyroid Cancer

All cancer tumors of this type are classified as Stage IV as it is a rapidly spreading malignancy.

Stage IVA: Cancer has spread to nearby areas even if it has not attacked the lymph nodes or other sites.

Stage IVB: It has spread beyond the thyroid and perhaps reached the lymph nodes but no further.

Stage IVC: It has spread to other parts of the body.

HOW IS THYROID CANCER DIAGNOSED?

There are several ways doctors diagnose Thyroid Cancer:

Physical examination: The doctor will examine your neck to look for changes in your thyroid. The physical examination will accompany questions about your family history and lifestyle to assess the risk factors.

Thyroid function blood tests. The pituitary gland in our brain produces a hormone called the Thyroid Stimulating Hormone (TSH), pushing the thyroid to release its hormones into the bloodstream. Measuring TSH levels reveal the thyroid’s health.

Thyroid tissue sample. A sample tissue of the thyroid is taken for a biopsy using fine-needle aspiration.

Genetic testing. Some types of medullary thyroid cancers are due to inherited genes, so genetic testing is a valuable tool for detecting thyroid cancers.

Ultrasound and other imaging tests: Imaging the thyroid with the help of high-frequency sound waves create a picture of the thyroid, which helps doctors examine it for abnormalities. Signs doctors look for include calcium deposits or uneven borders around a nodule. Other imaging tests may include CT and MRI scans.

Radioiodine scans: A small volume of radioactive iodine is administered to the patient as a pill or injected into a vein. The thyroid gland slowly absorbs the iodine, and a special camera scan is taken to see which parts of the thyroid are radioactive. Tumors in the thyroid reveal diminished radioactivity, whereas healthy cells show more radiation. The former is called cold nodules though not all cold nodules are cancerous. But the scan reveals the presence of tumors.

Note: Typically, the patient could be on a low-iodine diet before administration, so the thyroid absorbs it quickly, and the scan picks up the cancerous cells. The body flushes out the radioactive iodine after a few days.

TREATMENTS FOR THYROID CANCER

Depending on the type of thyroid cancer, its spread and the degree of malignancy, doctors will choose the treatment. Most thyroid cancers can be cured with timely treatment.

Thyroidectomy is a surgery to remove a portion of the thyroid or all of it. Post-surgery, the patient undergoes blood tests to determine the full extent of cancer elimination:

• The thyroglobulin test measures the amount of protein made by healthy and differentiated thyroid cancer cells.
• The calcitonin test measures the amount of calcitonin, a hormone that medullary thyroid cancer cells produce.
• The carcinoembryonic antigen test measures the level of carcinoembryonic antigen, a chemical released by medullary thyroid cancer cells.

Thyroid lobectomy: It involves removing one portion of the thyroid and is usually done in cancers that are slow growing, with no suspicious nodules or signs in the lymph nodes.

Note: Papillary and follicular carcinomas can usually be treated with surgery supported by radioactive iodine treatment (read below).

Lymph node removal in the neck: Because the thyroid is located in the neck, if cancer has spread to the lymph nodes, parts of it are removed for testing.

Radiotherapy: Radiation beams are aimed at cancer cells to kill them. It is usually employed when other treatments are not effective.

Chemotherapy: Different chemotherapy drugs are used singly or in combination, as pills or injections. It is effective to combat aggressive cancers such as anaplastic thyroid cancer.

Heat and cold treatment: This procedure uses heat and cold to kill cancer cells that have travelled to other organs such as bones, lungs etc.

Radiofrequency ablation: Electrical energy is precision-targeted at cancer cells, killing them.

Cryoablation: Cancer cells are killed using extreme cold gas that freezes them to death and is usually used on small malignant areas in the thyroid.

Alcohol ablation: Also called ethanol ablation, it injects alcohol into small areas of thyroid cancer and shrinks the malignant cells. It is an alternative when the patient cannot undergo major surgery.

Targeted therapy drug. This method is an option to treat advanced thyroid cancers, and it attacks particular chemicals in the cancer cells and forces them to die. The targeted drugs can be taken as pills or injected and come in different forms.

Radioactive iodine treatment: A radioactive form of iodine, as a capsule or liquid, is introduced into the body orally to kill thyroid cancer cells that might remain after surgery. It is effective only for papillary and follicular thyroid cancers.