thyroid Flashcards
What histological features are seen in papillary thyroid cancer
Orphan Annie nuclei
psammoma bodies
Psammoma bodies also seen in ovarian cancer and meningioma
Why can follicular thyroid cancer not be diagnosed on FNA
Needs capsule or vascular invasion, so can only be seen at thyroidectomy
What is the complication of Hurthle cell variant FTC
Does not take up RAI
What cells do medullary thyroid cancer arise from
What needs to be screened for
What is the treatment for MTC
Parafollicular c cells
Need to be screened for MEN2
Tx is surgery as far as possible
What features distinguish FAP from Gardners syndrome
Extra teeth
Colorectal adenomatous polyps, osteomas (skull & mandible), desmoid tumours, desmoid cysts, sebaceous cysts
What is Turcot syndrome
AD
Colonic polyps associated with CNS tumours (ependymomas and medulloblastomas)
Increased risk of thyroid/adrenal/BCC
What is Cowdens syndrome and what is the lifetime risk of thyroid cancer
AD PTEN mutation - hamartoma syndrome
30-40% lifetime risk of thyroid cancer (follicular, then papillary)
Also breast, endometrial, colorectal, melanoma
How is a T1 thyroid cancer defined
T2
tumour <2cm
T1a = <1cm
T1b = 1-2cm
T2 = 2-4cm
How is a T3 thyroid cancer defined
T3a - >4cm but limited to thyroid
T3b - extra thyroid extension
How is a T4 thyroid cancer defined
T4a - Local invasion into trachea, larynx, oesophagus, recurrent laryngeal nerve
T4b - Invasion into prevertebral fascia, mediastinal vessels or carotids
How is thyroid nodal staging defined
N1a - Involvement of level 6 or 7
N1b - involvement elsewhere
When is cross sectional imaging indicated for thyroid cancer
T3-4 disease ie evidence of local invasion or tumour >4cm
What are the indications for a hemithyroidectomy
T1a (<1cm) - T2 differentiated thyroid cancer
What are the indications for a total thyroidectomy
T3-4
Nodal involvement
Extra-thyroid spread, multifocal disease
High risk features
Pre-RAI - distant mets
What are the indications for radioactive iodine
Post total thyroidectomy
Tumour >4cm (T3)
>T1b with unfavourable characteristics (Tall cell, Columnar, Insular, Diffuse sclerosing papillary cancer, Poorly differentiated)
Gross extra-thyroidal extension
Distant metastases
Recurrence
RAI not indicated if all of:
Tumour <1cm unifocal or multifocal
Classic papillary or follicular variant of papillary or follicular thyroid cancer
No vascular invasion AND no extra-thyroid extension
what are the RAI doses and indications
1.1Gbq - T1b-T3, N0 with R0 resection
3.7GBq - T4 or N1 disease or metastatic disease
5.5GBq - recurrence disease
What needs to be done ahead of radio-iodine treatment
Stop Breast-feeding ≥ 8 weeks before RAI and do not resume
Sperm banking – esp if likely to have 2+ high dose RAI
Low-iodine diet (<50mcg/day) for 2 weeks before RAI
Avoid sea-food, iodised salt & ‘red’ food colouring. Eggs, butter & cheese
No iodine IV contrast for 8 weeks before treatment
No Amiodarone for a year prior to RAI
What precautions need to be taken after RAI?
Pt
Avoid constipation – to reduce bowel dose
Drink fluids, suck sweets (dry mouth) – to reduce bladder and salivary gland dose
Others
Visitors – none <16 years, max. 20-60 mins at distance
No close contact with pregnant women or children for up to 3 weeks
Sleep alone for one week
No public transport /crowded places
Double flush toilet for 1 week
Avoid incontinence pads / store for time
Pregnancy
Avoid pregnancy for 6 months after or fathering a child for 4 months
Increased risk miscarriage within 1yr
What are the side effects of RAI?
Acute
Discomfort / swelling over neck and salivary glands (sialadenitis)
Fatigue
Nausea
Change in taste
Cystitis / gastritis
Late
Dry mouth (RI goes to salivary gland)
Sialoadenitis and lacrimal gland dysfunction
Radiation lung fibrosis – if lots of lung mets
2nd malignancy (0.5%)
Risk is highest with high cumulative dose – e.g. >18.5GBq
Leukaemia, Salivary gland, Breast, Bladder, Colon
Reduce Male Fertility – if ≥2 high dose I131 treatments.
Women unaffected (dose <6Gy) but pt mustn’t be pregnant at time of treatment and shouldn’t become pregnant for 6mths (men shouldn’t father a child for 6wks)
What are the outcomes of a dynamic risk stratification?
USS & Thyroglobulin
Low risk - If Suppressed & Stimulated Tg <1 & US neck normal:
Aim TSH 0.3 - 2
Int risk - Tg 0.2-1 and sTg 1-10, Neck US: non-specific changes or Stable LN <1cm:
Aim TSH 0.1- 0.5 for 5-10 years
High risk - Suppressed Tg >1 or Stimulated Tg >10, rising Tg, residual disease on imaging:
Aim TSH <0.1
What are the indications for EBRT to the thyroid
Following RAI / Non-iodine-avid disease
Macroscopic disease after surgery
Recurrent neck disease not amenable to surgery
Palliation of metastases
What is the treatment for metastatic thyroid cancer
Surveillance & TSH suppression
RAI following total thyroidectomy - likely 5.5Gq dose
Systemic treatment with TKI - lenvatinib
What are the side effects of lenvatinib
Htn (Aim <140/90), proteinuria, Long QT - monitor
Skin toxicity and palmar-plantar syndrome
When is a neck dissection indicated in the management of thyroid cancer
Level VI neck dissection if node positive
Prophylactic level VI/VII neck dissection – consider if node neg, but high risk features
Age>55
Tumours >4cm (T3)
Extra-thyroidal disease
What must be done before surgery in medullary thyroid cancer
Exclude phaeochromocytoma - 24hr urine catecholamines and metanephrines, and plasma metanephrines
What is the management of medullary thyroid cancer
≤2cm -> Total thyroidectomy + central node dissection
If central nodes +ve -> ipsilateral lateral ND
If lateral nodes +ve -> selective ND (II-V)
> 2cm -> Total thyroidectomy + central ND + prophylactic bilateral selective ND II-V
When is EBRT indicated for medullary thyroid cancer
Primary RT - if inoperable disease
Adjuvant RT - Locally advanced disease, multiple involved LNs, or raised calcitonin post op indicative of residual disease
What is the treatment for metastatic medullary thyroid cancer
Assess for RET mutation
Thyroidectomy and further surgery as needed
TKI - cabozantinib (SE - risk of fistulation), selpercatinib 2nd line if RET mutation
What mutation should be tested for in anaplastic thyroid cancer
What is the treatment
B-raf V600E
Surgical resection
Palliative RT: AP POP: 40Gy in 20# or 20Gy in 5#
Dab/tram if B-raf mut
If early (stage 4A) - can be treated with surgery and adjuvant ChemoRT (H&N fractionation)
What proportion of hyper-PTHism is due to parathyroid carcinoma
1-2%
What gene is associated with parathyroid carcinoma
HRPT2 (CDC73)
What defines a T3 thyroid cancer
> 4cm & limited to thyroid (T3a) or locally invasive into strap muscles (T3b)
What thyroid cancer is most likely following radiation exposure
Papillary
