Thyroid for Dummies (18 page)

This procedure is done several times over several days. Complications include pain in the thyroid area and fever. This treatment is likely to become more and more common as doctors gain experience with it.

Benign cysts

A nodule that is filled with fluid shrinks when a needle is inserted and the fluid is removed. Unfortunately, the cyst often fills right up again. Repeated removal of the fluid sometimes cures the problem. An alternative approach is to inject ethanol into a cyst, the same procedure as injecting into a solid nodule. You can also choose to keep the cyst and leave it alone if you are willing to live with it.

Warm or cold nodules

Nodules that do not produce excessive thyroid hormone and are not cancer are sometimes treated with thyroid hormone in an attempt to shrink the nodule. Little evidence exists to show that this treatment works, however.

And, as giving too much thyroid hormone can cause bone loss or an abnormal heartbeat, many endocrinologists no longer recommend thyroid suppression.

Warm and cold nodules are examined every six months or every year. Should the nodule grow, a fine needle biopsy is done again. If the second diagnostic needle aspiration definitely rules out cancer, the nodule is left alone.

Ignoring Small Nodules

Every so often, a test such as an ultrasound of the neck reveals one or more very small nodules on the thyroid. Even the best specialists probably cannot feel a nodule that is less than one centimetre in size. The ultrasound may 12_031727 ch07.qxp 9/6/06 10:46 PM Page 88

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detect a nodule that is as small as 2–3mm across. One of these tiny, tiny nodules found by accident is referred to as an
incidentaloma
(a thyroid specialist’s agonising attempt at humour).

Most consultants monitor these nodules at regular intervals and try to leave them well alone as long as they are not growing in size.

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Chapter 8

Coping with Thyroid Cancer

In This Chapter

ᮣ Understanding how thyroid cancer starts

ᮣ Recognising the types of thyroid cancer

ᮣ Knowing and treating the stages of cancer

ᮣ Ensuring proper long-term follow-up

C
ancer
is a word that evokes a number of images, none of which are particularly positive. Although uncommon, people do die of thyroid cancer so this chapter explains what thyroid cancer is, how it grows, how it’s treated, and how to follow up after treatment if you or a loved one has thyroid cancer.

The facts and figures in this chapter help put thyroid cancer into perspective.

Researchers estimate that as much as 6 per cent of the world’s population has cancer of the thyroid gland. Based on this percentage, about 3,600,000

people in the United Kingdom may have evidence of thyroid cancer. Yet in the United Kingdom, out of every one million women, 23 are diagnosed as having thyroid cancer each year, compared with nine new cases for every one million males. In England and Wales, this figure adds up to approximately 900

new cases recognised each year, with 250 recorded deaths. This evidence suggests that the vast majority of people with thyroid cancer live and die without ever knowing that it existed. The cancer is only detected when the thyroid is carefully examined under a microscope which typically occurs after someone notices symptoms, such as a lump.

Thyroid cancer does not appear anywhere near the top of the list of causes of death in the United Kingdom, as it represents only around 1 per cent of all cancers. This figure suggests that compared to most other cancers thyroid cancer is one of the least dangerous. In fact, the long-term outcome is very favourable after treatment, with the 10 year survival rate approaching 90 per cent. No-one wants to have cancer. However, if you had to have cancer, this cancer could seem like one of the better ones to choose. However, between 5–20 per cent of people with thyroid cancer develop recurrences, and up to 15 per cent develop secondaries – where the cancer spreads to other parts of the body. Therefore, this cancer needs to be taken very seriously.

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The relatively benign course of most thyroid cancers (see the section

‘Identifying the Types of Thyroid Cancer’ later in this chapter for the different types of thyroid cancer) makes it difficult to say which treatment is best.

Perhaps certain treatments are very effective, or perhaps any number of treatments work just as well because the disease itself is so mild. For this reason, opinions on how to treat thyroid cancer differ among thyroid specialists.

Treatment is now more straightforward than it used to be, thanks to the recent development of national, evidence-based guidelines for the management of thyroid cancer in adults. These guidelines are recommendations from the British Thyroid Association and the Royal College of Physicians of London, and are designed to help thyroid specialists select the best treatment for each individual patient. These guidelines are available for download from: www.british-thyroid-association.org

Determining What Causes

Thyroid Cancer

John is 40 years old and has noticed a lump in the front of his neck on the left side. His family has no history of thyroid cancer. The lump is painless and moves when he swallows. He doesn’t know how long he’s had it. John goes to see his doctor, who requests thyroid function tests and finds that the TSH

and free T4 are normal. He refers John urgently to the thyroid specialist clinic where a thyroid scan shows that the area of the nodule on John’s thyroid does not take up any radioactivity – it’s a
cold
nodule. John’s endocrinologist then performs a fine needle aspiration biopsy (refer to Chapter 4). The pathologist examines cells from John’s thyroid gland under a microscope and diagnoses a papillary cancer, which is the most common type of thyroid cancer.

The thyroid surgeon recommends removing the whole thyroid gland (total thyroidectomy) while carefully retaining the tissue around the parathyroid glands and the recurrent laryngeal nerves that pass along the thyroid. The surgery goes well and no other suspicious nodes or nodules are found during the procedure.

John has no other treatment initially. After three weeks, he has a TSH test.

The result is very high indicating that very little thyroid tissue remains in his body (so the pituitary gland produces lots of TSH in a fruitless attempt to increase production of thyroxine hormone). He has another scan that shows no uptake of radioactive iodine except for in a small area of the thyroid tissue that was left intact by the surgeon. John is given a large dose of radioactive iodine to eliminate that small bit of tissue. A follow-up scan shows that all the thyroid tissue is gone. John is placed on thyroid hormone replacement and continues to visit the clinic on a regular basis. John will probably live a normal life span with no further trouble associated with the thyroid cancer other than the periodic visits for follow-up.

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John’s story is similar to that of most people who develop thyroid cancer, with the cancer first showing itself as a thyroid nodule (check out Chapter 7). Keep in mind that the vast majority of thyroid nodules are not cancerous, however.

Our understanding of why cancer occurs is getting clearer and clearer. We know that certain genes (part of our hereditary make-up) called
oncogenes
cause a cell to grow and divide without controls. Oncogenes exist in all of our cells. Just exactly what switches on certain oncogenes so they are active is not clear, but possibilities include a mistake in cell division (a mutation), some chemical or radiation in the environment, or the effects of a virus.

Human chromosome (our DNA) also contains other genes called
tumour suppressor genes
. Studies suggest that some people lack these tumour suppressor genes and are therefore more likely to develop cancers.

The best-known initiator of thyroid cancer is irradiation (being exposed to radiation), which is the source of many cancers in children living in the area of the Chernobyl nuclear accident in what is now Ukraine. The children drank milk from cows that ate the grass upon which radioactive substances fell – including radioactive iodine, during the reactor core accident. Within just a few years, many of these children had multiple sites of cancer in their thyroid glands. Adults exposed to radioactive iodine also developed thyroid cancer, though not as often as children, as a growing thyroid gland is more sensitive to radioactive damage.

Children who receive neck and face irradiation as an old-fashioned treatment for benign conditions such as acne or enlarged tonsils also develop thyroid cancer. In this case, the cancer occurs as many as 40 years later.

This chapter also discusses cancers of the thyroid that run in families, especially the cancer called
medullary thyroid cancer
.

Identifying the Types of Thyroid Cancer

A pathologist identifies thyroid cancer according to the appearance of the tissue that he or she examines under a microscope. If a nodule is diagnosed as cancer, identifying the particular type of cancer is important, since each one follows a different course. Treatments that work for one type of thyroid cancer may not work at all for a different sort of tumour.

Although you don’t need to know how to identify these types of cancer –

that’s the pathologist’s job – a basic understanding of the different types of cancer helps you to know what the future holds if a thyroid cancer is identified. When your doctor tells you the name of that cancer, you have an idea of what to expect.

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How a pathologist identifies a cancer

A pathologist looking at thyroid cancer cells

suggests that it has invaded that area –

under a microscope looks for a number of abnor-

examples are thyroid cells in a lymph gland,

malities that separate normal tissue from can-

in bone, or in the lung.

cerous tissue. He or she has studied thousands

Cancerous cells that are mature, and closely

of tissue slides and knows the appearance of the

resemble the type of cell from which it arose,

tissue when it’s found in a person whose clinical

are described as differentiated. This is a good

course suggests cancer compared with a

sign, as differentiated cancers are normally less

person who has a benign clinical course. The

aggressive than non-differentiated cancers,

key things that the pathologist looks for are:

which are immature and bear little resemblance

ߜ A malignant appearance to the tissue, to the types of cell from which they arose.

which means very large, abnormal looking

Papillary and follicular thyroid cancers are good

cells containing abnormal looking parts.

examples of differentiated cancers.

ߜ The presence of even, normal looking tissue

in an area where it doesn’t belong, which

While the descriptions for each type of thyroid cancer are true for most people with that type of cancer, exceptions do exist. Once in a while, someone with the most aggressive type of thyroid cancer finds that their cancer isn’t as aggressive as expected. In the same way, once in a while, a more benign form of thyroid cancer (based on its appearance) takes a more aggressive turn. Medicine is not an exact science.

Papillary thyroid cancer

Papillary thyroid cancer
is the most common form of thyroid cancer, accounting for more than 70 per cent of thyroid cancers seen in both adults and children. Fortunately, this form of thyroid cancer also tends to take a benign course, as it is differentiated (meaning it isn’t very aggressive). Although the cancer spreads to the local lymph glands in the neck as often as half the time, this spread doesn’t seem to make the cancer more aggressive.

The most important characteristics of papillary thyroid cancer are that it ߜ Rarely spreads away from the neck.

ߜ Is diagnosed most commonly between the ages of 30 and 50.

ߜ Is found in females three times as often as in males.

ߜ Is the thyroid cancer most often associated with radiation exposure.

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ߜ Concentrates radioactive iodine, which is useful if treatment is with radioactive iodine.

ߜ Is likely to be on a more aggressive course in people over the age of 45, especially if the tumour is larger than 1 centimetre.

ߜ It’s especially mild in younger people, in whom it rarely causes death.

Follicular thyroid cancer

Follicular thyroid cancer
makes up another 20 per cent of all thyroid cancers.

This cancer is a little more aggressive than papillary cancer, but still usually takes a benign course. It does not tend to spread locally to lymph glands, but goes to bone and the lungs more often than papillary cancer. This cancer’s main features are that it

ߜ Is diagnosed most often between the ages of 40 and 60.

ߜ Affects females three times as often as males.

ߜ Concentrates radioactive iodine.

ߜ Invades blood vessels, accounting for its tendency to go to distant sites.

ߜ Is usually more aggressive in older people.

Another cancer that follows a course similar to follicular cancer, but has a different appearance under the microscope, is called a
Hurthle cell tumour
. It does not tend to concentrate radioactive iodine, so this is not a useful form of treatment.

Medullary thyroid cancer

Medullary thyroid cancer
makes up only about 5–10 per cent of all cancers of the thyroid gland.

This cancer does not arise in the cells that produce thyroid hormones; rather, it arises in another type of cell found in the thyroid, called the
C cell
. The C