Not Enough Cells: How Insufficient Cytological Specimens Are Mirrored by Reporting Systems - Journey from the Bethesda to the WHO Reporting Systems

Background: Pap classes have been replaced by organ-specific reporting systems in recent decades; however, part of the cytological specimens is insufficient. The present review summarizes how different organ-specific systems define the insufficient category: both quantitative and qualitative criteria are used. In addition, the sample volume may be evaluated in certain specimens. Summary: The reasons for an insufficient sample may vary and depend either on the lesion itself or the sampling procedure. Key Messages: The management recommendations for insufficient specimens improve communication between cytopathologists and treating physicians.