Pathology of the Thyroid Gland Flashcards
What are the 4 main histological classifications of thyroid cancer?
Papillary - 6%
Follicular - 17%
Medullary - 3%
Anaplastic - 2%
What does differentiated thryoid cancer refer to?
Papillary and Follicular thryoid cancer
What do most DTCs do?
Take up iodine and secrete thyroglobulin - can act like normal thryoid cells
They are TSH driven
Decribe the rates of incidence of DTC in females and males.
Females - Rates increase from 15-40 then plateau
Males - Steady increase with age
How do DTC present?
Majority have palpable nodules
small % are chance findings
5% with local or disseminated mets
Give 5 points about Papillary thyroid cancer.
Associated with ionising radiation Usually solitary nodule Activates MAP kinase pathway Spreads via lymphatics - lungs, bone, liver and brain Associated with Hasimoto's thyroiditis
Give 4 points about Folicular thyroid cancer.
Associated with iodine deficiency
Usually single slow growing nodule - painless and non-functional
Mutations in PI3K/AKT pathway
Spreads haematogenously
What is the prognosis of DTC?
Generally good with 10 year mortality <5%
What Ix are used for suspected DTC?
USS guided FNA
Excision biopsy of lumh node
What are the clinical predictors of DTC?
New thyroid nodule 50 y.o Nodule increased in size Male Lesion >4cm History of head and neck irridation Vocal cord palsy - do pre-operative laryngoscopy
What exactly is the best management option for DTC?
Sub total thyroidectomy with RAI
What risk stratification tool is used post op for patients with DTC and why is this used?
A - age M - ets E - extent of primary tumour S - Size of primary tumour Used to stratify pts as low or high risk
When and why is whole body iodine scanning used?
Pts who have had total or sub-total thyroidectomy
Given low dose iodine capsule which will be taken up by thyroid and any DTC cells in the body to see of tumour all removed or mets
If uptake at thyroid bed >0.1% of ingested activity, what does the patient undergo?
Thyroid remnant ablation
then whole body iodine scan repeated to ensure uptake in thyroid bed now <0.1%
What can be used as a tumour marker in DTC?
Thyroglobulin - produced by DTC cells and normal thyroid cells but 0 from them as removed
What is a follicular adenoma?
Discrete solitary mass derived from thyroid follicular cells encapsulated by a surrounding collagen cuff –> very well circumbscribed
Is a follicular adenoma functional or non-functional?
Usually non-functional but can secrete thyroid hormones
Can medullary thyroid cancers be familial?
Yes (bilateral/ mulitcentric) or sporadic (solitary nodule)
What are medullary thryoid cancers composed of?
Spindle or polygonal cells arranged in nest, trabeculae or follicles
What can medullary thyroid cancers cause?
dysphagia
hoarseness
airway compromise
Give 4 points about Anaplastic thyroid cancer.
Undifferentiated and aggressive tumours
Usually older patients
May occur in pts with a history of DTC
Rapid growth and involvement of neck structures and death
What is the Thy scale and why is it used?
Thy 1 - insufficient sample
Thy 2 - benign
Thy 3 - atypia probably benign/ equivocal
Thy 4 - atypia suspicious of malignancy
Thy 5 - malignant
USS FNA used to provide a minimally invasive assessment of the likelihood of malignancy
What can cause primary hyperparathyriodism?
Adenoma involving a single gland or hyperplasia involving all glands
What causes secondary hyperparathyroidism?
Chronic hypocalcaemia causes compensatory over activity of parathyroid glands
What causes tertiary hyperparathyroidism?
Parathyroid activity becomes autonomous associated with hypercalcaemia
What causes hypoparathyroidism?
Usually post-operatively (removal by accident)
Rarely congenital absence - DiGeorge syndrome
Familial - associated with primary adrenal insufficiency and mucocutaneous candidiasis (AI basis)
What is the most common cause of hyper/hpothyroidism?
Autoimmune thyroid disease
What blood results would you expect to see from primary hyperthyroidism?
TSH low
T4/T3 high
What blood results would you expect to see from primary hypothyroidism?
TSH high
T4/T3 low
What blood results would you expect to see from secondary thyroid disease - pituitary gland failure?
TSH low
T4/T3 low
What blood results would you expect to see from secondary thyroid disease - TSHoma?
TSH high
T4/T3 high
What blood results would you expect to see from primary subclinical hypothyroidism?
TSH high
T3/T4 normal
Probably end up as overt hypothyroidism
Define hypothyroidism.
Results from a variety of abnormalities that cause insufficiet secretion of thryoid hormones
What causes primary hypothyroidism?
Iodine deficiency #1
AI - Hashimoto’s thyroiditis #1
Hereditary biosynthetic defects
Maternally transmitted antithyroid agents, iodides
Drug induced - amiodarone, lithium, thalidomide
What can cause secondary hypothyroidism?
Hypothalamic - congenital, infiltration, infection, malignancy
Pituitary - Panhypopituitarism, isolated TSh deficiency
What are the symptoms of hypothyroidism?
tiredness/ malaise Weight gain Cold intolerance Goitre Contipation Menorrhagia - later oligo or ammenorrhoea Arthralgia Myalgia Physchosis Poor libido
What are the signs of hypothyroidism?
Dry skin and dry thin hair Periorbital puffiness Pitting oedema Mental slowness Slow relaxing reflexes Carpal tunnel syndrome Hyperprolactinaemia bradycardia worsening of heart failure
What Ix should be used for hypothyroidism and what would their positive result be?
TSH high T4/T3 low Elevated CK Increases LDL cholesterol Hyponatraemia Hyperprolactinaemia Macrocytosis is typical – rule out a concurrent Vit B12 deficiency
What is Hashimoto’s Thyroiditis?
Gradual autoimmune destruction through antibody dependent cell mediated cytotoxicity, of the thyroid gland resulting in decreased thyroid hormone production
What autoantibodies are present in Hashimoto’s thyroiditis?
Anti-TPO (95%)
Anti-thyroglobulin antibody (60%)
TSH receptor antibody (10-20% - blocking)
How is hypothyrodism managed?
Restore normal metabolic rate gradually
younger pts - thyroxine at 50-100mcg daily
elderly with history of IHD - thyroxine at 25-50mcg daily - adjusted every 4 weeks according to response
In pregnancy the dose requirements of thyroxine increaaase by how much?
25-50% (increased TBG)
Who is usually affected by a myxoedema coma?
Elderly women with longstanding but frequently unrecognised/ untreated hypothyrodisim
How does a myxoedema coma present?
bradycrdia
type 2 respiratory failure
If a patient is on amiodarone, what should they have checked frequently?
TFTs
List some causes of Hyperthyroidism
Graves disease Multi-nodular goite Toxic nodule (adenoma) Subacute thyroiditis/De Quervains Post-partum thyroiditis Rare - iodine and medications (amiodarone, lithium, kelp)
List the symptoms of hyperthyroidism.
Tremor Palpitations Sweating Irritability Diarrhoea Weight loss Lighter/less frequent periods increased appetite intolerance to heat
What are the clinical signs of hyperthyriodism?
Tachycardia or AF Proximal muscle wasting goitre with bruit warm peripheries lid lag palmar erythema onycholysis
What are the treatment options for hyperthyriodism?
Carbimazole Propylthiouracil Fluid restriction Radioiodine and surgery may also be considered Symptom Tx = beta-blocker (Propanolol)
What positive investigations indicate Graves disease?
High T3/T4, low TSh
Anti-TPO +ve (70-80%
Anti-thyroglobulin +ve (30-50%)
TSH receptor antibody +ve (70-100% - stimulating)
What additional S&S are present in Grave’s disease?
Exophalmus Chemosis visual loss proptosis diplopia pretibial myxoedema
What may trigger De Quervains?
Viral infection - other symptoms ay be present - sore throat, fever, etc)
What blood results are seen in De Quervains?
T4 - high in early stage, low in late stage then normal
TSH - low in early stage, high in late stage then normal
What treatment is required for a thyroid storm?
ABCDE May require ventilation Lugol's iodine Glucocorticoids PTU beta-blocker fluids monitoring
How does a thyroid storm present?
Respiratory and cardiac collapse
Hypertermia
Exaggerated reflexes
What precautions should be followed if you are on radio-active iodine?
avoid close prolonged contact with children and pregnancy women
Avoid sharing a bed for x days
avoid pregnancy for 6-12 months
ensure not pregnant at start
high risk of hypothyroidism (esp. in Graves)
