Follicular thyroid carcinoma

Follicular thyroid carcinoma
Diagnosis in short
Micrograph showing a follicular thyroid carcinoma. H&E stain.
LM	bland thyroid cells invading through the (fibrous) capsule or lymphovascular invasion or distal metastases
LM DDx	follicular thyroid adenoma, papillary thyroid carcinoma follicular variant
Site	thyroid gland
Signs	thyroid nodule/mass
Prevalence	uncommon, female predominant
Prognosis	good
Treatment	surgical excision

Follicular thyroid carcinoma, abbreviated FTC, is an uncommon malignancy of the thyroid gland. It is also known as follicular carcinoma.

General

• Usually spread by the hematologic route.
  • PTC usually spreads via lymphatics.

Clinical

Medical school memory device 4 Fs:

• FNA NOT diagnosable.
• Far away mets (sometimes).
• Female predominant.
• Favourable prognosis.

Gross

• Encapuslated lesion +/-evidence of invasion through the capsule.

Images

• 

  FTC - gross. (WC/Euthman)

Microscopic

Features:

• Defined by either:
  1. Invasion through the capsule:
     • Should be all the way through.
       • 1/2 does not count.
       • Fibrous reaction does not count.
       • "Above the contour" does not count.
  2. Vascular invasion (all of the following):
     1. In a small vein (not a capillary), that is outside of the tumour mass.
     2. Tumour adherent to the side of the vessel.
     3. Tumour must be re-endothelialized.

Notes:

• Impossible to differentiate from follicular adenoma on FNA (no cytologic differences).
• Described as "over-diagnosed" ... misdiagnoses: PTC follicular variant, follicular adenoma, multinodular goitre with a thick capsule.

DDx:

• Follicular thyroid adenoma.
• Papillary thyroid carcinoma follicular variant.

Images

• 

  FTC - very low mag.

• 

  FTC - low mag.

• 

  FTC - intermed. mag.

• 

  FTC - high mag.

• 

  FTC - high mag.

• 

  FTC - very low mag.

• 

  FTC - low mag.

• 

  FTC - low mag.

• 

  FTC - intermed. mag.

• 

  FTC - intermed. mag.

• 

  FTC - high mag.

• 

  Metastatic FTC. (WC/Yale Rosen)

• 

  Metastatic FTC. (WC/Yale Rosen)

www

• Follicular thyroid carcinoma - several images (upmc.edu).

See also

• Thyroid gland.