Background

Question 1

Name the anatomic subdivisions/lobes of the thyroid.

Answer 1

Subdivisions/lobes of the thyroid:

Right lobe
Left lobe
Isthmus
Pyramidal lobe (in 50% of individuals is remnant of thyroglossal duct)

Question 2

In the thyroid follicle, what are the normal functions of the epithelial follicular cells and the parafollicular cells?

Answer 2

Epithelial follicular cells: remove iodide from the blood and use it to form T3 and T4 thyroid hormones

Parafollicular cells (C cells): lie just outside of the follicle cells and produce calcitonin

Question 3

What is the most common endocrine malignancy?

Answer 3

Thyroid cancer (TCa) is the most common endocrine malignancy, but is only 1% of all diagnosed malignancies.

Question 4

What is the estimated incidence of new TCa Dx and deaths in the United States?

Answer 4

There are an estimated 57,000 new Dx (3/4 women) and 2,000 deaths in 2017.

Question 5

What are the 3 main TCa histologies in decreasing order of frequency?

Answer 5

Differentiated (follicular-derived) thyroid carcinoma (DTCa) (∼94%) > medullary (2%–4%) > anaplastic (2%)

Question 6

What are the 3 subtypes of DTCa in decreasing order of frequency?

Answer 6

Papillary (90% of all TCa) > follicular > Hürthle cell carcinoma

Question 7

What is happening to the incidence of diagnosed papillary TCa?

Answer 7

The incidence of papillary TCa is increasing (by ∼20% over the past 50 yrs, largely driven by better surveillance/detection of smaller lesions).

Question 8

What is the typical age at Dx for follicular vs. papillary TCa?

Answer 8

Follicular incidence peaks at 40–60 yrs of age, whereas papillary peaks at 30–50 yrs of age.

Question 9

Is there a sex predilection for papillary or follicular TCa?

Answer 9

Yes. Both papillary and follicular TCa more commonly affect females than males (3:1).

Question 10

What is the strongest risk factor for papillary TCa?

Answer 10

RT exposure to the H&N as a child is the strongest risk factor for papillary TCa. There is no increased risk if exposure is after age 20 yrs. Most papillary cases are sporadic.

Question 11

Name 4 genetic disorders associated with papillary TCa.

Answer 11

Genetic disorders associated with papillary TCa:

Familial polyposis
Gardner syndrome
Turcot syndrome
Familial papillary carcinoma

Question 12

Name a genetic disorder associated with follicular TCa.

Answer 12

Cowden syndrome (PTEN gene mutation) is associated with follicular TCa.

Question 13

Medullary TCa arises from what precursor cell?

Answer 13

Medullary TCa arises from the calcitonin-producing parafollicular C cells.

Question 14

Name 2 genetic syndromes associated with medullary TCa.

Answer 14

MEN 2a and MEN 2b (RET gene mutation) are associated with medullary TCa.

Question 15

What % of medullary TCa is related to a genetic syndrome?

Answer 15

∼25% of medullary TCa is related to a genetic syndrome.

Question 16

Name the nerve that lies in the tracheoesophageal (TE) groove, post to the right/left thyroid lobes.

Answer 16

The recurrent laryngeal nerve lies in the TE groove.

Question 17

What are the primary, secondary, and tertiary lymphatic drainage regions of the thyroid?

Answer 17

Primary: central compartment (level VI or paralaryngeal and paratracheal), Delphian (prelaryngeal) LNs

Secondary: cervical, SCV, and upper mediastinal LNs (levels III–IV, VII)

Tertiary: upper cervical (level II)/retropharyngeal LNs