Histologic classification of glomerular diseases: clinicopathologic correlations, limitations exposed by validation studies, and suggestions for modification  Mark Haas, Maria P. Rastaldi, Fernando C. Fervenza  Kidney International  Volume 85, Issue 4, Pages 779-793 (April 2014) DOI: 10.1038/ki.2013.375 Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 1 Histologic features of active International Society of Nephrology/Renal Pathology Society (ISN/RPS) class IV-S (upper two panels) and IV-G (lower two panels) lupus nephritis. Active segmental (IV-S) lesions show segmental endocapillary hypercellularity, whereas in global (IV-G) lesions nearly all of the glomerular capillaries are largely occluded by endocapillary cells. In addition to segmental endocapillary hypercellularity, the upper right panel shows segmental fibrinoid necrosis, a frequent finding in IV-S lesions, with disruption of the glomerular basement membrane and an associated cellular crescent. Two segmental necrotizing lesions are also noted in the glomerulus at left in the upper left panel. Necrosis and crescents may also be seen in IV-G lesions (although less frequently than in IV-S), and in the lower left panel the glomerulus at right shows a small cellular crescent, as does the glomerulus in the lower right panel. The latter glomerulus also shows large, pink-staining subendothelial deposits (‘wire loops’), a frequent finding in active IV-G lesions. Jones silver methenamine stain (all photomicrographs); original magnification × 200 (upper left and lower left panels; bar=20μm) or × 400 (upper right and lower right panels; bar=40μm). Kidney International 2014 85, 779-793DOI: (10.1038/ki.2013.375) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 2 Glomerular immunoglobulin G (IgG) deposits in a case of lupus nephritis, International Society of Nephrology/Renal Pathology Society (ISN/RPS) class IV segmental (IV-S). Note the segmental paucity of deposits (arrow). Direct immunofluorescence with fluorescein isothiocyanate (FITC)–conjugated anti-human IgG. Scale bar=40μm. Kidney International 2014 85, 779-793DOI: (10.1038/ki.2013.375) Copyright © 2014 International Society of Nephrology Terms and Conditions

Figure 3 Histopathologic lesions correlating with worse clinical outcomes according to the Oxford classification for IgA nephropathy. The M, E, S, and T scores are shown in the upper left corner of each panel. Upper left panel shows mesangial hypercellularity (M1) with moderate tubular atrophy and interstitial fibrosis (T1). In the upper right panel, both glomeruli show mesangial hypercellularity (M1), and the glomerulus at right also shows segmental endocapillary hypercellularity (E1). There is minimal tubular atrophy and interstitial fibrosis (T0). In the lower left panel, there is mesangial hypercellularity (M1), and the glomerulus at right shows segmental sclerosis (S1). There is only a very mild degree of tubular atrophy and interstitial fibrosis (T0). In the lower right panel, the glomerulus that is not globally sclerotic shows segmental mesangial and endocapillary hypercellularity (M1, E1), as well as segmental sclerosis (S1). This glomerulus also shows a fibrocellular crescent, although crescents are not specifically scored in the Oxford classification. There is severe tubular atrophy and interstitial fibrosis (T2). Periodic acid–Schiff (PAS) stain, original magnification × 200 (all photomicrographs; bar=40μm). Kidney International 2014 85, 779-793DOI: (10.1038/ki.2013.375) Copyright © 2014 International Society of Nephrology Terms and Conditions