Cancer of the thyroid gland

Thyroid gland overview

The thyroid gland is an endocrine gland that makes the hormones that control your metabolism. The thyroid gland is located at the base of the neck, sitting over the trachea (your windpipe) it has two lobes, which are joined together by the isthmus.

The thyroid gland produces the hormones Thyroxine (T4) and Triiodothyronine (T3). These molecules include iodine, which you normally take with your food. Your body has an internal balancing system, to avoid over or under production of these hormones. This is centrally controlled by another gland inside your brain, called the pituitary. The pituitary gland produces the ‘Thyroid Stimulating Hormone’  (TSH), which controls the thyroid gland in a simple negative feedback way.

Any abnormalities in the production of the thyroid hormones can lead to hypothyroidism or hyperthyroidism. Hyperthyroidism is the condition that your thyroid overproduces thyroid hormones (or, if your taking too many thyroid tablets). You will normally feel overactive, with increase appetite, having increased metabolism, palpitations, insomnia, and you may notice weight loss. If you have hypothyroidism you will feel tired, lethargic and can put on weight easily. These conditions should be investigated and treated by your endocrinologist.

Cancer of the thyroid

Thyroid cancer is rare, however, its incidence is increasing due to more incidental small cancers found on routine thyroid ultrasound scans. In the majority of cases, is slow growing and has excellent prognosis.

Symptoms

In some cases, the patient is completely asymptomatic and thyroid cancer is discovered as part of a routine ultrasound scan. Other symptoms might include:

  • Lump at the front of the neck
  • Difficulty in swallowing
  • Difficulty in breathing
  • Voice changes

Thyroid cancer doesn’t usually affect thyroid hormone production.

Diagnosis

Your Head and Neck Surgeon will examine you and take a thorough medical history. He will feel your neck for lumps. A thyroid lump moves when you swallow; this is a good indication for your surgeon that the lump in your neck originates from your thyroid gland.

Investigations

  • Ultrasound scan: This is usually the first line investigation for thyroid lumps. It utilises a probe and sound waves to produce a picture of your thyroid gland and any lumps. The lumps are classified using the U classification (1-5). The chances of having thyroid cancer increase the closer you get to U5 (https://onlinelibrary.wiley.com/doi/pdf/10.1111/cen.12515).
  • Fine needle aspiration: This is a form of biopsy, but instead of tissue sample, only few cells are taken with the help of a syringe and needle. The cells are viewed under a microscope to find out if they are abnormal. It is usually done with under ultrasound guidance. Thyroid lumps are classified using the Thy classification (1-5). The chances of having thyroid cancer increase the closer you get to Thy5.
  • Rarely, in cases of confirmed thyroid cancer, a CT scan of your neck and thorax, and/or an MRI of your neck may need to be performed.

Types of thyroid cancer

There are four types of thyroid cancer:

  • Papillary (most common type, more common in younger women)
  • Follicular (less common type, more common in older people)
  • Medullary (rare type, sometimes familial)
  • Anaplastic (very rare, more common in older people and women, terrible prognosis – incurable)

Papillary and follicular cancers are called “differentiated thyroid cancer”, and they respond to treatment with radioactive iodine, because they look and act like normal thyroid cells and uptake iodine.

Cause

The cause of thyroid cancer is not known. Previous exposure to radioactive materials or neck radiotherapy is been considered a risk factor. Thyroid cancer incidence has increased 15 years following the Chernobyl disaster.

Treatment

The main treatment for thyroid cancer is surgery. This is aided by radioactive iodine. Occasionally, external beam radiotherapy and hormone therapy can be considered, but usually this is for advanced disease. Prognosis is excellent, with over 90% chance of cure. Even in cases of distant metastatic spread (which is rare), there is a good chance of disease control. Thyroid cancer can recur at any point in life; therefore long-term follow up is important. Prognosis remains good, even for recurrent disease. The exception is the anaplastic type of thyroid cancer, which is incurable and has a mean survival expectation of few months.

All patients who have been diagnosed with thyroid cancer will be discussed at a multidisciplinary team meeting (MDT).

Surgery

Surgery is the first line treatment for thyroid cancer. Occasionally (i.e. in cases of Thy3f) surgery can be both diagnostic as well as therapeutic. You may have only one of the two lobes taken out  – this is called a lobectomy or hemithyroidectomy. If all the thyroid gland is removed, the procedure is called total thyroidectomy. Following the procedure, the pathologist examines the specimen under the microscope.

The operation is carried out under general anaesthetic. Your Head and Neck Surgeon will cut the skin at the front of your neck, using a suitable skin crease. He will then identify your thyroid gland and remove either half of it (hemithyroidectomy or lobectomy) or all of it (total thyroidectomy), depending on the size and type of the cancer. The procedure is carried out using an intraoperative nerve monitor, to ensure protection of the recurrent laryngeal nerve – a nerve that is extremely useful for your speech and breathing. Following removal of your thyroid gland, your Head and Neck surgeon will suture the wound – the cosmetic result is usually excellent. If you have a hemithyroidectomy, you may be able to go home the same day. In cases of a total thyroidectomy, you may need to stay in the hospital for 24-48h, and this is mainly due to the need to monitor your calcium levels.

Possible complications

Like any other surgical procedure, the thyroidectomy has potential risks. Your Head and Neck surgeon will discuss these risks prior to your surgery, so that you can make an informed decision, weighing the potential benefits of having the procedure versus the risks. The most common complications are:

  • Bruising of the recurrent laryngeal nerve: Every effort is made to preserve this nerve intact. However, occasional temporary bruising can occur, and this results in your voice to sound weaker. It improves and resolves with time.
  • Pain
  • Bleeding
  • Infection
  • Damage to the parathyroid glands: Your parathyroid glands control the levels of Calcium in your bloodstream. There are usually 4 of these glands. In cases of total thyroidectomy, damage or removal of these glands means you may require calcium supplements, but this is usually only for a short time.
  • Following total thyroidectomy, you will need thyroid replacement therapy (thyroxine)

Radioactive iodine therapy

This treatment consists of swallowing a radioactive iodine capsule and the iodine is taken up by the thyroid gland. Radioiodine is used with differentiated thyroid cancer (papillary and follicular). The small dose of radiation is concentrated in the cancer thyroid cells and destroys them.

Follow-up and monitoring

You will be followed-up and monitored both by your endocrinologist and by your H&N surgeon. One important blood test that you may have is measuring your thyroglobulin. This is a protein that is produced both by normal thyroid cells and thyroid cancer cells (papillary and follicular). After surgery and radioiodine treatment, the thyroglobulin level is usually very low. If the amount of thyroglobulin in the blood is found high, this is a sign of disease relapse, and more treatment might be needed. Thyroglobulin is measured at least once a year.