Thy3a nodules with cytological atypia: True indeterminate or papillary thyroid carcinoma waiting for a full diagnosis?

The agreement of the different cytological categories used worldwide is a long lasting and highly debated topic. Although the systems are broadly similar, some differences still exist especially in grey areas, i.e. the poorly defined classes like Thy3a. Trying to reduce the interobserver variability, we limit the diagnosis of THY3a to cases with scanty atypia (SA), which is the first and most important pattern described by Van der Horst et al. and encompasses cases in which some atypical features are present but their interpretation can be influenced by cell scarcity, artefacts and cystic changes.