Consensus definitions for glomerular lesions by light and electron microscopy: recommendations from a working group of the Renal Pathology Society

In this paper, Mark Haas and colleagues present a comprehensive list of > 40 consensus definitions for light microscopy and > 50 consensus definitions for electron microscopy findings in glomeruli. The definitions are grouped according to substructure, are worded in detail and include tresholds. For instance, mesangial matrix expansion is defined as ‘Increased mesangial extracellular material with interspace width of > 2 mesangial cell nuclei, in one or more peripheral mesangial areas’. The definitions can be applied across the full spectrum of glomerular diseases and within the context of different scoring systems used for these diseases.

A standard for harmonization of terms in renal pathology reporting is very welcome because reproducibility of research findings is often hindered by intra- and interobserver agreement, precluding adequate prognostication and prediction. This study marks the first of many steps towards improving agreement with obvious advantages for upcoming research. Benefits extend to diagnostic practice, as this standard might improve communication between pathologists and promote interaction between pathologists and nephrologists.

There are some limitations: the system remains to be tested, it does not guarantee acceptance among renal pathologists worldwide and it is limited to human language (it is not a digital standard).