Papillary thyroid carcinoma Tall cell variant

• 5 - 10% of PTCs
•  Usually older age patients
•  Female more than males
•  Site of origin: Thyroid
•  Exceedingly rare at other sites (ectopic thyroid tissues)
•  Sporadic in most cases
•  Risk factors: same as most other variants of PTC
•  Ionizing radiation and pre-existing benign thyroid disease 
• The most common aggressive variant of PTC
• Extra-thyroidal extension and metastatic lymph nodes are commonly seen
•  Microscopy:
  • WHO 2017 definition: Tall cells (2 - 3x height / width cells) occupying ≥ 30% tumor
  • Well developed PTC nuclear features
  •  If tall cell features are > 10% but < 30%, the tumor should be designated as PTC with tall cell features
    • PTCs with tall cell features (≥ 10% tall cells) have worse prognosis than those without tall cells; more than 10% tall cells in a tumor should be reported in final pathology reports