Table 5. Definitions

Diffuse: A lesion involving most (≥50%) glomeruli
Focal: A lesion involving <50% of glomeruli
Global: A lesion involving more than half of the glomerular tuft
Segmental: A lesion involving less than half of the glomerular tuft (i.e., at least half of the glomerular tuft is spared)
Mesangial hypercellularity: At least three mesangial cells per mesangial region in a 3 micron thick section
Endocapillary proliferation: Endocapillary hypercellularity due to increased number of mesangial cells, endothelial cells, and infiltrating monocytes, and causing narrowing of the glomerular capillary lumina
Extracapillary proliferation or cellular crescent: Extracapillary cell proliferation of more than two cell layers occupying one fourth or more of the glomerular capsular circumference
Karyorrhexis: Presence of apoptotic, pyknotic, and fragmented nuclei
Necrosis: A lesion characterized by fragmentation of nuclei or disruption of the glomerular basement membrane, often associated with the presence of fibrin-rich material
Hyaline thrombi: Intracapillary eosinophilic material of a homogeneous consistency which by immunofluorescence has been shown to consist of immune deposits
Proportion of involved glomeruli: Intended to indicate the percentage of total glomeruli affected by lupus nephritis, including the glomeruli that are sclerosed due to lupus nephritis, but excluding ischemic glomeruli with inadequate perfusion due to vascular pathology separate from lupus nephritis