Key Points:
- The diagnostic performance of the tiered FNAC reporting system can be variable between different institutions
- Our results demonstrate higher rates of malignancy compared to other published series.
-Thy1 and Thy2 results (especially from cystic lesions) should be interpreted with caution and repeat testing performed if any other suspicious criteria.
- Individual centres should discuss FNAC cytology in a multidisciplinary team setting, and should quote local malignancy rates during patient counselling.
- It is prudent for all units performing thyroid diagnostics to control the factors that might lead to reporting variability.