Thyroid Gland and Tumours
Thyroid gland enlargement and tumours
The thyroid gland is located in the centre of the neck below the voice box. It consists of two lobes (left and right) and an isthmus connecting the two sides. It lies over the front of the windpipe shaping the thyroid like a butterfly. Occasionally patients have a pyramidal lobe which is found above the isthmus and is an embryological remnant of the path the thyroid takes as it originates at the back of the tongue and drops down into the neck. If this path fails to close it can form a cyst known as a thyroglossal duct cyst. A normal thyroid gland is small and not palpable (able to be felt) in the neck unless it is enlarged.
Benign Thyroid Lumps and Swellings
A thyroid goitre (see image above) is a general enlargement of the thyroid gland and can affect one lobe or the whole thyroid gland. It is a general term and encompasses a number of different conditions; the most common of which is a multinodular goitre. This is where the thyroid produces lots of small cysts or nodules within the gland causing it to enlarge. Causes of a goitre include an over or underactive thyroid, puberty, pregnancy, iodine deficiency, autoimmune conditions. These often do not require any treatment unless causing compressive symptoms or requiring continual medical treatment. Sometimes a goitre can be caused by a single large nodule or cyst and may only affect one part of the thyroid. Anyone with a thyroid enlargement should have a blood test to check their thyroid function.
Compressive symptoms of a goitre include:
- neck swelling
- difficulty breathing
- neck tightness
- swallowing problems
- sensation of choking when lying backwards
- coughing or voice changes (rare)
Depending on the size of the goitre and the symptoms, you may be offered a Hemithyroidectomy, also known as Thyroid Lobectomy (removing half the thyroid and isthmus), Isthmectomy (removing the middle part of the thyroid) or a Total Thyroidectomy where the whole gland is removed. Your surgeon will discuss the best option for you and your symptoms but the risks factors for each procedure are discussed below.
Thyroid cysts are simple cysts within the thyroid gland. They can be solitary or multiple and are benign. Cysts can get larger, remain stable in size or increase in size. They may cause compressive symptoms or a lump in the neck which may cause cosmetic changes. Large cysts can be drained but may recur and need to be surgically removed.
Thyroid nodules can be single or multiple. They will be graded on an ultrasound scan and may require a needle biopsy. They can be non-cancerous or cancerous and if there is any concern on the ultrasound, a needle test will help determine if it is benign, a possible cancer or a cancer. Thyroid nodules can present with compressive symptoms or as a lump in the neck.
Thyroid cancer is increasing in incidence due to better detection rate and is currently the most common endocrine cancer. It has an incidence rate of 9:100 000. There are 5 main subtypes of thyroid cancer, two of which make up around 90% of cases and have an excellent prognosis – the survival rate is over 95% twenty years following diagnosis. Thyroid cancers usually present with a painless lump in the neck, either in the thyroid gland or in a lymph node. Very rarely they can present with pain, a hoarse voice or problems swallowing. Any thyroid cancer or patients with a suspicion of thyroid cancer should be discussed at a thyroid multidisciplinary team (MDT) meeting of cancer specialists. Robert Hone and Ali Al-Lami are both members of the East Kent thyroid and parathyroid MDT.
Papillary thyroid cancer is the most common thyroid cancer accounting for around 70% of all thyroid cancer. Papillary thyroid cancer is usually “well differentiated” which means it resembles the tissue that it arises from and grows slowly and does not behave in an aggressive way, remaining stable in size. These have an excellent prognosis with survival of over 95% at twenty years. Occasionally, they are poorly differentiated – they grow much faster, are more aggressive and unfortunately have a worse prognosis. If papillary thyroid cancer spreads, it is usually to the lymph nodes in the neck and these can be treated relatively easily.
Follicular thyroid cancer is the second most common thyroid cancer and makes up around 20% of all thyroid cancers. Prognosis is also excellent at over 95% at 20 years. However this cancer tends to spread through the blood stream meaning cancer deposits at distant sites are more common and if this happens, follicular thyroid cancer is harder to treat. Depending on the treatment you receive a blood marker called thyroglobulin can be used to monitor papillary thyroid cancer.
Medullary thyroid cancer is rare and makes up around 5% of all thyroid cancer. It can have a genetic disposition and patients with this form of cancer are screened for genetic changes that may make them more susceptible to this type of thyroid cancer or more likely to develop tumours in other areas of the body. Medullary thyroid cancer can be monitored after treatment using a blood tumour marker called calcitonin (a chemical in the blood produced by medullary thyroid cancer).
Lymphoma of the thyroid gland also accounts for around 5% of thyroid cancers. It usually grows quite quickly and responds very well to treatment. Once diagnosed you will be referred to the lymphoma multidisciplinary team meeting and your care taken over by the Haematology Department for treatment, which is usually chemotherapy and/or radiotherapy.
Anaplastic thyroid cancer is rare and makes up less than 1% of all thyroid cancer. Unfortunately, this cancer is very aggressive, and prognosis is very poor. It grows very quickly – invading other structures and sends cancer deposits to other areas of the body meaning surgery is often not possible and chemotherapy and radiotherapy rarely have any effect on this cancer. Sadly, less than 10% of people survive more than a year following the diagnosis, which can be difficult to obtain.
The best treatment for thyroid cancer is surgery to remove the tumour. Depending on the individual risk factors, the type, stage and size of the cancer, additional treatment may be offered. This can be in the form or radioactive iodine treatment and in rare instances radiotherapy with or without chemotherapy. Systemic chemotherapy has a limited role in thyroid cancer and is only occasionally used in specific cases. A regular blood test to look for a blood marker called thyroglobulin and antibodies called thyroglobulin antibodies may also be indicated to look for the presence of any remaining thyroid tissue. If these markers are increasing it may suggest the presence of residual or recurrence of your thyroid cancer and further investigations or treatment may be indicated.
Investigations to determine diagnosis
It is important that anyone with a thyroid lump undergoes an ultrasound with or without a needle biopsy. (See scan image below). The ultrasound will determine the nature of the lump/swelling. The ultrasound should be graded according to the U grade as outlined in the British Thyroid Association (BTA) guidelines. This grades the thyroid/nodules from U1 to U5 – these are outlined below:
• U1 – Benign (non-cancerous) normal thyroid gland
• U2 – Benign (non-cancerous) nodule
• U3 – Indeterminate nodule (around 20% chance of a cancer)
• U4 – Suspicious nodule (around 50% chance of a cancer)
• U5 – Thyroid cancer (99% of this nodule being a cancer)
As per the BTA guidelines, any nodule over one centimetre in size which is U3, any U4 or any U5 nodule should have a fine needle aspiration cytology (FNAC) test to look at the cells within the nodule to further determine the risk of the nodule being a cancer. This uses a fine needle to remove some cells which can be looked at under a microscope to assess if they are worrying or not. If there is a concern about lymphoma or anaplastic thyroid cancer, a core needle biopsy should be performed. This uses a larger needle to remove tissue for immunological analysis and will hopefully give a diagnosis although rarely an open biopsy of the tissue may be needed. The FNAC test can be categorised by the Thy grading system which is outlined below:
• Thy 1 – Non diagnostic sample and may need to be repeated
• Thy 2 – Benign
• Thy 3a – Indeterminate nodule with some atypical cells, this carries around a 20% chance of being a thyroid cancer
• Thy 3f – Indeterminate nodule with follicular cells, this carries around a 30% chance of being a thyroid cancer
• Thy 4 – Suspicious for thyroid cancer which carries roughly a 60% risk of cancer
• Thy 5 – Thyroid cancer with over 99% being a thyroid cancer.
Any thyroid nodule of Thy 3 and above should be discussed at the thyroid MDT and is usually recommended to be removed surgically to confirm the diagnosis and treat the nodule or cancer. The surgery offered depends on the Thy grade, size, position and appearance of the nodule or nodules. In some instances, depending on the patient and other factors, ultrasound surveillance with or without another needle biopsy may be offered to monitor the nodule.
If thyroid surgery is recommended, this nearly always requires an overnight stay in hospital. In very rare instances, it can be done as a day case with the patient discharged home the same day. Rarely, 2 nights or more in hospital are needed if you develop a low calcium level that needs treating and is difficult to normalise. The operation is performed under general anaesthetic. Depending on the type of thyroid swelling, reason for the operation or location of the lump, this be performed as either a Hemithyroidectomy, a Total Thyroidectomy or an Isthmectomy:
• Hemithyroidectomy – half/one side of the thyroid is removed
• Total Thyroidectomy – all of the thyroid is removed
• Isthmectomy – only the middle portion of the thyroid is removed
The patient will usually have a drain (a small plastic tube to collect excess fluid) left in the wound which will be removed the following morning and skin sutures (which many be dissolvable) or skin clips which need to be removed at the GP surgery after 48 hours and steri-strips applied.
Patients are seen in clinic for a post-operative follow up appointment after around 2 weeks if the procedure is for a cancer or 4-6 weeks if it is benign. A repeat nasal endoscopy will be performed in clinic to check vocal cord movement. A thyroid function test should be taken at around 10 weeks post operatively to check the function of the remaining gland and that the level of thyroid hormone replacement is adequate.
If you have been diagnosed with thyroid cancer, you will be discussed at the East Kent thyroid MDT following the procedure, and you may be asked to take higher doses of thyroxine to suppress the amount of thyroid stimulating hormone produced in the brain.
Radioactive Iodine Treatment
If you have thyroid cancer, following your surgery and discussion at the East Kent thyroid MDT, you may be offered radioactive iodine treatment. This is offered to patients who are deemed to be at a higher risk of their thyroid cancer returning. This treatment involves taking some radioactive iodine which is absorbed by any remaining thyroid cells and thyroid cancer cells. The radioactive iodine subsequently kills these cells hopefully removing any remaining thyroid cancer cells from your body. You will need to stay in hospital for a few days so we can collect all the radioactive waste you produce. It is recommended you do not see children for up to 2 weeks after the iodine treatment. There are very few side affects and the treatment is very safe and effective. After the iodine you will be scanned to look at the uptake in the body. A year after treatment, you will be risk stratified with an ultrasound and blood test and placed within low, intermediate and high risk groups which will determine further investigations and follow up.
Risks of thyroid surgery
• Like any procedures, there is a risk of bleeding and infection, the incidence of this is around 1-2%
• You will have a small scar at the front of the neck (see images to the right). The second image is a scar at 6 weeks post-operatively. We aim to hide this within a skin crease so it is less noticeable. The scar will be around 4-5cm in length when healed but if your thyroid is very large it may need to be longer
• There is a risk of damage to the nerve to the voice box (called the recurrent laryngeal nerve). If the nerve is damaged you may suffer with a hoarse voice. This risk is around 1% and half of these will be temporary. If the whole of the thyroid gland is removed there is roughly a 1 in 10,000 chance both could be damaged which can lead to some breathing problems immediately after the operation, but this is exceptionally rare
• Hypothyroidism (low thyroid levels) occurs in up to 5% of patients having half the thyroid removed as the remaining half cannot cope with the body’s demands. In this instance, you will need to take thyroxine (the natural hormone produced by the thyroid gland) to supplement your needs. If all the thyroid is removed, you will need thyroid supplements on a life-long basis
• Hypocalcaemia (where the bodies calcium level drops below normal) can occur if all the thyroid gland is removed. This occurs temporarily in up to 10% of patients with less than 1% requiring long term (over 3-6 months of treatment). This occurs because the blood supply to the parathyroid glands comes from the thyroid and is interrupted – causing temporary dysfunction of the gland. You will need a minimum of two calcium checks after a Total or Completion (where the remaining half of the thyroid gland is removed) Thyroidectomy.
• Further surgery may be required following a Hemithyroidectomy for the following reasons:
– if worrying pathology is found
– it grows significantly
– it becomes symptomatic with compressive symptoms
– a new lump
– problems swallowing or a hoarse voice