Thyroid Conditions Flashcards
What are differentiated thyroid cancer?
Differentiated thyroid cancer (DTC) refers to papillary and follicular variants
Who is affected by DCTs?
Can affect any age group - childhood to elderly.
In females, rates increase from 15-40 then plateaus
In males, rates steadily increase with age
Are DCTs associated with any diet or lifestyle risk factors?
- Not associated with diet, other proven malignancies, family history, smoking or other lifestyle factors
- Other than clusters associated with nuclear incidence, the overall incidence is constant at present
What is papillary carcinoma?
- Derived from follicular epithelium
- Associated with Hashimoto’s
- Associated with ionising radiation
What are the genetic associations with papillary carcinoma?
- Activation of MAP kinase pathway
- Rearrangements of RET or NTKR1
- Activating point mutation in BRAF
- Mutation of ras
What is follicular carcinoma?
- Derived from follicular epithelium
- Higher incidence in females
- Higher incidence at 40-50 years
- Incidence slightly higher in regions of iodine deficiency
What are the genetic associations with follicular carcinoma?
- Mutations in PI3K/AKT pathway
- Mutations in ras family
- Translocation involving Pax8 and PPAR𝛾1
Describe the histology of papillary carcinoma.
- Can be multifocal
- Often cystic
- May be calcified - psammoma bodies
Describe the histology of follicular carcinoma.
- Diagnosis depends on invasion of the capsule or vascular invasion
- Classed as minimally invasive or widely invasive
- Widely invasive: more solid architecture, less follicular architecture, more mitotic activity
- Minimally invasive: (most common) follicular architecture (well differentiated), may have part surrounding capsule, difficult to distinguish from adenoma
What does this histology slide indicate?
Papillary Carcinoma
What does this histology slide indicate?
Follicular Carcinoma
Describe the spread of papillary carcinoma
- Papillary carcinomas tend to spread via lymphatics e.g. cervical lymph node metastases
- Haematogenous spread is uncommon but if occurs spread is usually to the lung, bone, liver and brain
Describe the spread of follicular carcinoma.
- Rarely lymphatic spread, propensity for haematogenous spread (bones, lungs, liver)
- Uncommon to have multicentric disease
What is the typical presentation of DTCs?
- Majority present with palpable nodules
- Small percentage are chance findings on histological section of thyroidectomy tissue
- Approx. 5% present with local or disseminated metastases
- Local effects e.g. hoarseness, dysphagia, cough suggest advanced disease
What are the investigations for DTCs?
- TSH, US
- Confirmation: usually US-FNA, can involve excisional biopsy of lymph node
- No role for isotope thyroid scan (in diagnosis), CT or MRI
- Pre-operative laryngoscopy if vocal cord palsy suspected clinically
Who are in the low risk group for surgical management of DTCs?
Age <50 years, tumour <4 cm
What is the surgical management for the low risk DTCs?
Thyroid lobectomy + biopsy, thyroidectomy following biopsy results if needed
Who is in the high risk group for DTCs?
Stage Thy3 or higher on FNA (atypical)
What is the surgical management for someone in the high risk group of DTCs?
- Subtotal/total thyroidectomy
- Consider radioactive iodine
Who gets a whole body iodine scan? and why?
- Used in patients who have undergone sub-total or total thyroidectomy
- Usually performed 3-6 months post-op
- Used to determine incomplete incision or present of occult metastases, and therefore inform need for further investigation/treatment
Why is RAI ablation used?
- Ablate residual thyroid tissue in order to destroy occult microfoci
- Remove residual thyroid tissue which may be a source of Tg and therefore confound the levels during follow-up
- Permit predictively useful scanning in whole body scans and subsequent high dose therapy if required
- Small but significant incidence of acute myeloid leukaemia, no convincing evidence of increase in incidence of other solid tumours
What follow up should be done for someone with DTCs?
- In both the low and high-risk groups, measure TSH and Tg every 6 months for first 5 years, then annually for next 5 years
- Consider discharge after 5 years if low risk
- To minimise risk of recurrence patients are treated with suppressive doses of levothyroxine (sufficient to suppress TSH below the normal range)
- For low-risk group, TSH should be kept in lower range of normal (0.4-4 mU/L), whereas in the high-risk group TSH should be kept <0.1 mU/L and fT4 below 25
- Thyroglobulin (Tg) is the protein precursor of T4/T3, made by thyroid follicular epithelial cell - can be used as ‘tumour marker’
What is the management of recurrent DTCs?
- Can be detected clinically, by rising Tg, or by imaging
- Recurrence in cervical lymph nodes is more common in papillary cancer
- Haematogenous spread to lungs, bone or brain more common in follicular lesions
- Usually, patients undergo whole body scan to determine ability to take up iodine with a view to RAI
- Difficult group are those with rising Tg but negative whole body iodine scan - management options include PET scan to allow targeted treatment, and systemic anti-cancer therapy e.g., sorafenib and Lenvatinib
What is thyrotoxicosis?
the clinical, physiological, and biochemical state arising when the tissues are exposed to excess thyroid hormone