Follicular Carcinoma of Thyroid

Question 1

what is it?

Answer 1

2nd most common thyroid carcinoma
Usually a single nodule
o Slowly enlarging, painless and non-functional
o Rarely lymphatic spread but propensity for haematogenous spread – bone, lungs and liver
A differentiated thyroid cancer (DTC), most take up iodine and secrete thyroglobulin and are driven by TSH
Spread tends to be haematogenous

Question 2

what % of thyroid carcinomas are follicular?

Answer 2

10-20%

Question 3

how are they classified?

Answer 3

Diagnosis is dependent on invasion of the capsule or vascular invasion
Classified as minimally invasive or widely invasive FTC

Question 4

who gets it?

Answer 4

more common in females

40s and 50s

Question 5

growth pattern

Answer 5

Widely invasive
o More solid architecture
o Less follicular architecture
o More mitotic activity

Minimally invasive
o Follicular architecture (well differentiated)
o May have part surrounding capsule
o Difficult to distinguish from adenoma
o Follicular adenoma vs carcinoma – need vascular or capsular invasion
o Usually treated by thyroid lobectomy – if significant vascular invasion consider a total thyroidectomy
o Most present U3 lesion and diagnosed by lobectomy
o Capsular invasion can’t be detected by FNA

Question 6

how is it investigated?

Answer 6

Ultrasound and guided FNA of the lesion
Can involve excision and biopsy of the lymph node
Isotope biopsy, CT and MRI are not beneficial
Pre-operative laryngoscopy if vocal cord palsy is clinically suspected

Question 7

post-operative

Answer 7

Check calcium within 24 hrs
Calcium replacement initiated if corrected if falls below 2mmol/l
IV calcium for calcium levels below 1.8mmol/l or symptomatic
Discharge on T3 or T4
Whole body iodine scan
o 3-6 months post-op
o T4 stopped 4 weeks before
o T3 stopped 2 weeks before
o rhTSH far better so don’t need to stop T3/T4
o TSH should be > 20 for best results
o Scan informs treatment decisions