Thyroid Cancer

John P. Christodouleas and Vincent J. Lee

Background

Name the 4 anatomic subdivisions/lobes of the thyroid.

Subdivisions/lobes of the thyroid:

Right lobe
Left lobe
Isthmus
Pyramidal lobe

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

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

What is the most common endocrine malignancy?

Thyroid cancer (TCa) is the most common endocrine malignancy.

TCa represents what % of all diagnosed human cancers?

TCa is rare and only represents 1% of all diagnosed malignancies.

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

Main TCa histologies (in decreasing order of frequency): follicular-epithelial derived (FED) (~94%) > medullary (2%–4%) > anaplastic (2%)

What are the 3 subtypes of FED TCa in decreasing order of frequency?

Subtypes of FED TCa (in decreasing order of frequency): papillary > follicular > Hurthle cell carcinoma

What is the incidence of papillary TCa in autopsy series?

30%–40% of cases have “microcarcinomas.”

What is happening to the incidence of diagnosed papillary TCa?

The incidence of papillary TCa is increasing (approximately by 15% over the past 40 yrs).

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

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

Is there a gender predilection for papillary or follicular TCa?

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

What is the strongest risk factor for papillary TCa?

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.

Name 4 genetic disorders associated with papillary TCa.

Genetic disorders associated with papillary TCa:

Familial polyposis
Gardner syndrome
Turcot syndrome
Familial papillary carcinoma

Name a genetic disorder associated with follicular TCa.

Cowden syndrome is associated with follicular TCa.

Medullary TCa arises from what precursor cell?

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

Name 2 genetic syndromes associated with medullary TCa.

MEN 2a and MEN 2b are associated with medullary TCa.

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

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

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

The recurrent laryngeal nerve lies in the TE groove.

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

Primary: central compartment (level VI), TE groove, delphian nodes
Secondary: cervical/supraclavicular nodes
Tertiary: sup mediastinal/retropharyngeal nodes

Workup/Staging

What % of palpable thyroid nodules are malignant?

Only 5% of palpable thyroid nodules are malignant.

In a pt with low TSH and a nodule that shows uptake by I-123 or Tc-99 scan, what is the likely Dx?

Adenomas commonly present with low TSH and increased uptake on I-123 or Tc-99 scans.

Which FED subtypes are difficult to distinguish from adenomas on FNA?

Follicular and Hurthle subtypes are difficult to distinguish from adenomas. Histologically, they show only follicular structures. Papillary TCa shows both papillary and follicular structures that help to distinguish it from adenomas.

What pathologic criteria must be met to make the Dx of Hurthle cell TCa?

The Dx requires hypercellularity with >75% Hurthle cells

Only gold members can continue reading. Log In or Register to continue