Follicular thyroid carcinoma

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

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]
        • 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:[2]

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

See also

References

  1. ↑ SR. 17 January 2011.
  2. ↑ Sobrinho-Simões, M.; Eloy, C.; Magalhães, J.; Lobo, C.; Amaro, T. (Apr 2011). "Follicular thyroid carcinoma.". Mod Pathol 24 Suppl 2: S10-8. doi:10.1038/modpathol.2010.133. PMID 21455197.
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