ENDOCRINOLOGY - THYROID CANCER Flashcards
What are the 3 types of thyroid malignancies?
Differentiated thyroid carcinoma - papillary, follicular and hurthle cell cancers
Medullary thyroid carcinoma
Anaplastic thyroid carcinoma
What’s the most common form of thyroid cancer?
Papillary thyroid carcinoma - 70%
What are the features of papillary thyroid carcinomas?
Usually presents between 35-40 years of age
3 times more common in women
Most often presents as micropapillary thyroid carcinoma with an excellent long-term prognosis
Spreads locally to the neck, compressing trachea and possible involving the recurrent laryngeal nerve
Metastasis most often occur in lung, bone, mediastinal lymph nodes, pelvic area, brain and liver
What are the features of follicular thyroid carcinoma?
Tends to occur in areas of low iodine
3 times more common in women and most often presents between 30 and 60 years of age
May infiltrate the neck and commonly metastasise to lung and bones
What are the features of hurthle cell carcinoma?
May present from 20 but most often between 50-60 years
Impossible to distinguish benign from malignant tumours on fine need aspiration
Surgical excision is the main treatment
More aggressive than other thyroid cancers with a high incidence of metastasis and lower survival rate
What are medullary thyroid carcinomas?
Arise from parafollicular C cels in thyroid - calcitonin producing
75% occur sporadically and 23% hereditary (autosomal dominant)
Elevated serum calcitonin is a maker of the presence of this cancer
What is anaplastic thyroid carcinoma?
The most aggressive thyroid tumour and one of the most aggressive cancers in humans
ATC arises from follicular cells of the thyroid gland but does not retain any of the biological features of the original cells
Peak incidence is in 60-70s
Most often it develops from a pre-existing well-differentiated thyroid tumour which had undergone additional mutational events
Causes compression symptoms
50% of patients present with distant metastases, mostly in lungs but also bones, liver and brain
Mean overall survival is often <6 months whatever treatment is performed
What are most thyroid lymphomas?
Non-Hodgkin lymphomas
What are some risk factors for thyroid cancer?
Thyroid nodules in…
Children
Adults <30
Patients with a history of neck or head radiation
FHx thyroid cancer
How common are thyroid nodules?
Very! 50% of the population have them but only 10% can actually feel it
More common in women and incidence increases with age
What are some common causes of benign thyroid nodules?
Thyroid adenoma - a basic single follicular adenoma… can undergo mutation in its FSH receptor and progress to a toxic adenoma (also benign)
Multinodular goitre
Hashimoto’s thyroiditis
Thyroid cys
What is a toxic adenoma?
this is when the adenoma becomes hyper functioning so produces lots of T3 and T4 irrespective to TSH
What are some features of thyroid nodules which may sway one to think its malignant?
If its non-functional i.e. doesn’t produce any thyroid hormones
Irregular shape
What is needed for a definitive diagnosis of a thyroid nodules?
Fine needle aspiration
Outline the approach to someone who presents with a thyroid nodule/goitre?
Thyroid stimulating hormone levels - if normal or high then order ultrasound
Ultrasound thyroid gland to assess anatomy of thyroid gland, nodule and adjacent structures
If it meets criteria, give fine needle aspiration
What are suspicious ultrasound findings of a thyroid nodule?
Nodule >1cm
Solid nodule
Hypoechoic
Large or rapidly growing nodule
Microcalcification
Central vascularity
Nodule that is taller than wider
What are the criteria for fine needle aspiration?
If suspucious findings on ultrasound
If none of these then we just monitor the nodule and repeat the ultrasound in a few months time
What is fine needle aspiration?
a thin, hollow needle is inserted into the mass for sampling of cells that, after being stained, are examined under a microscope. - cells sent to cytology
How do we classify a nodule after fine needle aspiration?
Using Bethesda classing:
1. Non-diagnostic result - insufficient sample so repeat FNA
2. Benign adenoma
3. Atypical or follicular of undetermined significance e- monitor
4. Follicular neoplasia
5. Suspicious for malignancy
6. Malignancy
When is a thyroidectomy indicated?
Class 4,5 and 6 of Bethesda classes after FNA
How do you investigate a thyroid nodule when bloods show low TSH?
Give thyroid scintigraphy - chemical molecule such as iodine given and is taken up by the thyroid gland
- if it doesn’t take it up then it is non-functional nodule (i.e. not producing thyroid hormones) - raises suspicion of cancer so needs ultrasound and FNA
Or…
- nodule takes up iodine - this is called a hot nodule and is rarely cancerous. Measure T3 and T4 - if these are normal with low TSH then its subclinical hyperthyroidism and if they’re high with low TSH then its hyperthyroidism (likely to be a toxic adenoma because its a nodule and takes up a lot of iodine)
How does radioactive iodine therapy work?
Taken up by the thyroid and destroys the cells in the thyroid gland. This has the effect of reducing the amount of thyroxine made by the thyroid gland and may also reduce the size of the gland
Who should not have radioactive iodine treatment?
Pregnant women
Breast feeding women
Anyone regularly vomiting or incontinence
People with active thyroid eye disease - may worsen the eye disease unless steroids are given at the same time
Why is it important to have regular thyroid blood tests are radioactive iodine treatment?
Because a common longer term side effect is hypothyroidism
