Ten percent tall cells confer the aggressive features of the tall cell variant of papillary thyroid carcinoma.

Background: The tall cell (TC) variant of papillary thyroid carcinoma (PTC) is more aggressive than classic PTC, but the percentage of TC necessary to diagnose this variant has been debated. We aimed to better determine what percentage of TC correlates with a more aggressive phenotype.

Methods: Cases from 2005 to 2010 that were the TC variant of PTC or PTC with TC features were identified and compared with classic PTCs.