Follicular thyroid carcinoma

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

• 

  Metastatic FTC. (WC/Yale Rosen)

• 

  Metastatic FTC. (WC/Yale Rosen)

www:

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

See also

• Thyroid gland.