Understanding thyroid cancer
Understanding thyroid cancer
Specialist breast and endocrine surgeon, Dr Francois Malherbe, tells us more about the types of thyroid cancer and how they are treated.
Function of the thyroid
The thyroid is a gland in the neck with the main function of producing hormones integral to cell metabolism. Pathology of the thyroid gland can broadly be divided into two groups: disorders of thyroid function (hormone production) and disorders of thyroid form (gland enlargement, nodules and thyroid cancer).
Hormone abnormalities are mostly treated by medical endocrinologists while thyroid enlargement, thyroid nodules and thyroid cancer are managed by surgeons.
Increase in diagnosis
Thyroid nodules are very common, but symptomatic patient-detected nodules are rare. Up to 65% of the general population will have impalpable, asymptomatic thyroid nodules. Five percent of people will have a palpable thyroid nodule if a doctor examines their neck and even less will present with a self-detected nodule.
The increased use of high-definition neck ultrasound and CT scans, mainly done for other reasons, have led to a significant increase in the detection of incidental asymptomatic thyroid nodules. The increased detection rates led to increased numbers of biopsies and with that the diagnosis of thyroid cancer.
In South Korea, for instance, there has been a 15-fold increase in thyroid cancers from 1993 to 2011. Mainly because of a government-funded screening programme.
What is important is that the numbers of patients dying from thyroid cancers have been stable over this time. This means that although more cancers are being diagnosed, most of these patients would have received unnecessary invasive treatments for a cancer that would never have had any clinical impact. Meaning they would have died of another cause and not because of their thyroid cancer.
This phenomenon is called over-diagnosis and it remains a challenge for doctors to be able to find and treat aggressive cancers early, and be less aggressive in the management of indolent slow-growing tumours.
Analysis of specific mutations in thyroid and other tumours will in future help us make better treatment decisions. Unfortunately, the first generation of these tests, for thyroid cancers, are not widely available and they are very expensive limiting their widespread use.
Presentation and diagnosis
Thyroid cancer usually presents as a nodule in the thyroid gland. The thyroid nodule could either be patient detected or discovered incidentally on a scan, done for another reason as discussed previously.
Other less frequent methods of presentation include: palpable lymph glands in the neck away from the thyroid gland, voice change (hoarseness), problems swallowing, and difficulty in breathing.
It’s important to understand that not every thyroid nodule needs a biopsy. The way the lump looks on ultrasound helps us to decide which patient needs a biopsy.
If indicated, a fine needle biopsy helps us to decide if a nodule is cancerous or suspicious of a cancer.
Some thyroid cancers can’t be diagnosed with a fine needle biopsy alone and a thyroid operation, usually a thyroid lobectomy where one half of the thyroid is removed, might be necessary for the diagnosis of thyroid cancer.
Groups of thyroid cancers and treatment
There are different types of thyroid cancers and they are all treated slightly different. The three main groups of thyroid cancers are well-differentiated, moderately differentiated and poorly differentiated. Well-differentiated thyroid cancers are the most common as a group. With papillary thyroid cancer being the most common, making up 85% of thyroid cancers overall. Papillary thyroid cancers have the best prognosis with 97% of patients being alive 10 years after diagnosis. This compares very well to other poor prognostic cancers, like for instance pancreas cancer. In a group of individuals with pancreas cancer, only 7% of them will be alive five years after diagnosis.
The other two well-differentiated thyroid cancers are follicular and Hurthle cell thyroid cancers. Both these cancers still have a good prognosis but worse compared to papillary thyroid cancer.
Well-differentiated thyroid cancers are treated with a combination of surgery, thyroid hormones and radioactive iodine.
Medullary thyroid cancer is a moderately differentiated cancer that can be part of genetic cancer syndromes. It’s mainly treated by removing the thyroid gland and often neck lymph nodes. Thyroid hormone and radioactive iodine are not part of the cancer treatment in patients with Medullary thyroid cancer.
Anaplastic thyroid cancer is a poorly differentiated cancer with a poor prognosis with mainly surgical management if detected early. It presents as a rapidly growing thyroid mass, often in older women. Fortunately, it’s quite rare, representing only about 2% of thyroid cancers.
In general, the clear majority of patients diagnosed with thyroid cancer do very well and relatively few die from the disease. This is mainly because most of the cancers are well-differentiated and often a papillary thyroid cancer.
MEET THE EXPERT – Dr Francois Malherbe
Dr Francois Malherbe FCS(SA) is a specialist breast and endocrine surgeon working at Groote Schuur and UCT Private Academic Hospitals in Cape Town.
Header image by Freepik
References
https://www.thyroid.org/patient-thyroid-information/ct-for-patients/february-2017/vol-10-issue-2-p-10-11/
Ito, Y., et al. (2018). “Overall survival of papillary thyroid carcinoma patients: a single-institution long-term follow-up of 5897 patients.” World journal of surgery 42(3): 615-622.
Olson, E., et al. (2019). “Epidemiology of thyroid cancer: a review of the national cancer database, 2000-2013.” Cureus 11(2).