Thyroid Cancer Flashcards
How common is thyroid cancer compared to other endocrine cancers?
It is the most common cancer of the endocrine system
How common is thyroid cancer compared to all other cancers?
It is a relatively uncommon malignancy
What is the incidence of thyroid nodules in the general population?
Approx 5%
What gender are thyroid nodules more common in?
Women (2.5 : 1 female to male ratio)
What is the prevalence of thyroid cancer in a solitary nodule or in a multi-nodular thyroid?
10-20%
What increases the prevalence of thyroid cancer in a solitary nodule or multi-nodular thyroid?
Irradiation to the neck
What are the most common types of thyroid cancer in the young?
- Papillary
- Follicular
- Medullary
What is the most common type of thyroid cancer in the elderly?
-Anaplastic
What geographical locations have a higher incidence of thyroid cancer?
Regions that were exposed to the Chernobyl disaster, or Japanese populations following atomic bomb detonations
What are the risk factors for thyroid cancer?
- Benign thyroid conditions
- Radiation exposure
What benign thyroid conditions can increase the risk of thyroid cancer?
- Goitre
- Thyroiditis
- Thyroid adenomas
What might cause radiation exposure to the thyroid?
- Treatment for childhood cancer
- High levels after environmental incidents, such as the Chernobyl disaster
What increases the risk of thyroid cancer in those exposed to radiation?
Low levels of iodine
On what basis are thyroid cancers classified?
Morphologically
What are the morphological classifications of thyroid cancer?
- Papillary
- Follicular
- Anaplastic
- Hurthle cell
- Medullary cell
- Lymphoma
What morphological classifications of thyroid cancer are considered to be ‘differentiated’?
- Papillary
- Follicular
What % of cases of thyroid cancer are differentiated thyroid cancers?
90%
What mutations are associated with papillary thyroid carcinoma?
- BRAF
- Overexpression of cyclin D1
What % of papillary thyroid carcinomas are associated with BRAF mutations?
40%
What signalling pathway may be disrupted in papillary and anaplastic cancers?
pRb signalling pathway
Why might the pRb signalling pathway be disrupted in anaplastic thyroid cancers?
Due to upregulation of E2F1
What cells do papillary thyroid tumours arise from?
Thyroid follicular cells
Describe the distribution of papillary thyroid tumours
They are unilateral in most cases, and are often multifocal within a single thyroid lobe
How big are papillary thyroid tumours?
They vary in size, from microscopic cancers to large cancers
What might large papillary thyroid tumours invade into?
- The thyroid capsule
- Contiguous structures
How do papillary thyroid tumours metastasise?
They tend to invade the lymphatics
Vascular invasion and haematogenous spread is uncommon
Describe the spread of follicular carcinoma?
Although mostly encapsulated, it commonly has microscopic vascular and capsular invasion
Is there lymph node involvement in follicular thyroid carcinoma?
There is usually no lymph node involvement
What can follicular thyroid carcinoma be difficult to distinguish from?
It’s benign counterpart, follicular adenoma
Why can follicular thyroid carcinoma be difficult to distinguish from follicular adenoma?
As the distinction is made based on the presence or absence of capsular or vascular invasion, which cannot be evaluated by FNA
What % of thyroid cancers are medullary thyroid cancers?
10%
What cells do medullary thyroid cancers arise from?
C-cells of the thyroid
What do medullary thyroid cancers secrete?
Calcitonin
What are the forms of medullary thyroid cancer, in terms of aetiology?
- Sporadic
- Hereditary
What % of medullary thyroid cancers are the sporadic form?
80%
What % of patients with familial medullary thyroid cancer have a mutated RET proto-oncogene?
85%
What other condition is associated with a mutated RET proto-oncogene?
MEN 2A (multiple endocrine neoplasia type 2) - almost all people with the condition have the mutated gene
What % of thyroid cancer are anaplastic?
5%
What are the features of anaplastic thyroid carcinoma?
- High mitotic rate
- More likely to invade local structures such as lymph nodes
How do most patients with thyroid cancer present?
- Painless lump in thyroid
- Cervical or supraclavicular lymphadenopathy
Are patients presenting with thyroid cancer hypo-, eu-, or hyperthyroid?
Almost all patients are euthyroid
What are the features of the thyroid lump in thyroid cancer?
- Moves with swallowing and tongue protrusion
- Usually firm and non-tender
What can produce a hoarse voice in thyroid cancer?
Compression of the recurrent laryngeal nerve
Are dysphagia and stridor common presentations of thyroid cancer?
No, they are rare
How can thyroid cancer cause dysphagia and stridor?
They result from a large tumour compressing the upper airway and oesophagus