Anaplastic Thyroid Carcinoma

Overview (WHO Criteria changed in 2022)

High Grade and Anaplastic Thyroid Carcinomas
Tumor type High Grade Follicular Cell-Derived Thyroid Carcinomas (HGFCTC) Anaplastic Thyroid Carcinoma (ATC)
Differentiated High Grade Thyroid Carcinoma (DHGTC) Poorly Differentiated Thyroid Carcinoma (PDTC)
WHO definition
  • Not PDTC
  • ≥1 of the following:
    • mitotic index ≥ 3 per 10 high power fields
    • necrosis
  • Not papillary carcinoma
  • Solid/trabecular/insular architecture
  • ≥1 of the following:
    • mitotic index ≥ 3 per 10 high power fields
    • necrosis
    • convoluted nuclei
  • anaplastic (undifferentiated)
  • may have focal areas of healthy differentiation or differentiated carcinoma
    		•
    IHC
  • CK+ in 100%
  • TTF-1, PAX8, TG + in 100% (markers of thyroid follicular cell differentiation)
  • Ki67 low
    		•
  • CK+ in 75%
  • TTF-1+ in 0-30%, PAX8+ in 55-80%, TG in 0-5%
  • Ki67 median 50%
    		•
    Mutations
  • RAS 6-30%
  • BRAF 53-81%
  • TP53 4%
    		•
  • RAS 44-48%
  • BRAF 6-9%
  • TP53 16%
    		•
  • RAS 27%
  • BRAF 38% (BRAF V600E IHC is 95% sens, 100% spec for mutations)
  • TP53 62%
    		•
    RAI avidity 42% 65% No, but is avid on FDG-PET
    Distant metastases (5y) 48% 60% 75-80%
    Disease-specific mortality (5y) 32% 30% >80%
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