Differentiated Thyroid Cancer

Question 1

Some epidemiological facts regarding papillary thyroid cancer
(risk factors, prognosis)

Answer 1

• 70-80% of thyroid carcinomas
• peak incidence 30s-40s
• most important risk factor = childhood radiation exposure
• other risk factors: family history, Werner/Cowden syndrome, Carney complex, familial polyposis
• 95% ten year survival rate

Question 2

Papillary thyroid cancer- histological appearance (pathognomonic signs)

Answer 2

calcifications
psammoma bodies (concentric lamellated calcific structures)
squamous metaplasia & fibrosis

Question 3

Histological variants of PTC?

Answer 3

classical PTC
follicular PTC
tall cell
columnar 
hobnail (tends to occur in older patients, prognosis less favourable)

Question 4

What % of people with PTC have lymphatic mets? What are the two most common sites of lymphatic mets?

Answer 4

30-40% of people
3-5% metastatic at time of diagnosis
lungs and bones are two most common sites

Question 5

Is lymphadenectomy routinely performed for PTC?

Answer 5

Nope

Intra-operatively checking for suspicious LN- then can take out if suspicious

Question 6

What is the most common genetic mutation seen in PTC?

Answer 6

BRAF V600E

V= valine
E= glutamic acid

20% of patients with PTC have RET proto-oncogene

Question 7

What other conditions is RET proto-oncogene associated with?

Answer 7

pheochromocytoma, FMTC, Hirschsprung’s disease

Question 8

According to 2015 ATA guidelines, what are the recommendations for surgery based on size of tumour?

Answer 8

> 4 cm: total thyroidectomy
1-4 cm: total thyroid vs lobectomy
<1 cm: observe unless there are high risk features (extrathyroidal extension, lymphatic mets, etc)

Question 9

What is a thyroid microcarcinoma?

Answer 9

papillary thyroid cancers <1 cm in size

-may be multifocal and are usually clinically silent until thyroidectomy for another indication

Question 10

Epidemiology facts about follicular carcinoma.

Answer 10

10-20% of thyroid cancers

• females>males
• usually older population than PTC (40-60s)

Question 11

Is radiation a risk factor?

What is the best prognostic factor?

Answer 11

Radiation is NOT risk factor

Age is best prognostic factor

Question 12

Genetic mutations associated with Follicular carcinoma

Answer 12

PAX 8/PPARgamma genetic mutations

Question 13

Most common route of spread for follicular thyroid cancer?

Answer 13

hematogenous
F - far away

LN spread in 10% of cases only
>80% of follicular carcinomas will take up iodine

Question 14

What is a minimally invasive follicular carcinoma?

Answer 14

follicular neoplasms that capsular invasion but no vascular invasion

Question 15

Hurthle cell carcinoma

Answer 15

5% of all thyroid carcinomas

• likely follicular origin, considered DTC
• less than 10% of HCCs take up iodine

Question 16

Management of Hurthle cell carcinoma (HCC)

Answer 16

diagnostic thyroid lobectomy at minimum

usually advocate for total thyroid

Question 17

Indications for total thyroidectomy in Hurthle cell carcinoma

Answer 17

• DTCs >4 cm in size
• extrathyroidal extension
• regional or distant mets
• contralateral nodules/prior irradiation/familial DTC
• patient preference

Question 18

What is the most common tumour to metastasie to thyroid gland?

Answer 18

Renal cell carcinoma

Other less common primaries: breast, lung, GI tract, melanoma, sarcoma

Question 19

What are some prognostic scoring systems for thyroid malignancy?

Answer 19

AGES, AMES, MACIS

AGES
A- age (low risk if women <50 years, men <40 years)
*most important prognistcator
G- grade
E- extrathyroidal disease
S- size of tumour (>4 cm bad)

AMES
A- age
M- mets
E- extrathyroidal invasion
S- size of tumour

MACIS
M- mets
A- age
C- completeness of resection
I- invasion of extrathyroidal structures
S- size of tumour

Question 20

How is age incorporated into TNM system?

Answer 20

if patient is less than 45 years old and does not have mets = Stage I (still favourable prognosis if younger)

Question 21

What is the follow-up protocol after thyroidectomy for recurrent thyroid cancer?

Answer 21

Low risk:
Annual:
-physical exam
-Neck ultrasound at 6-12 months then frequency depends on patient factors
-TSH levels
-serum Tg and anti-Tg levels (if total thyroidectomy) q12-24 months

High risk:
same stuff as above, except do the Tg and anti-Tg levels q6-12 months instead