Light micrograph showing glomerular amyloidosis

Light micrograph of glomerular amyloidosis shows nodular amorphous material (arrows) extending from the mesangium into the capillary loops and narrowing or closing the capillary lumens. Amyloid deposits are pale when H&E stain is applied and do not stain with PAS or with methenamine silver stain. They are usually more amorphous than those of diabetic nephropathy, which are positive on PAS and silver stain. The diagnosis of renal amyloidosis relies upon the demonstration of amyloid fibrils by electron microscopy or green birefringence with Congo red staining.

Light micrograph of a normal glomerulus. There are only one or two cells per capillary tuft, the capillary lumens are open, the thickness of the glomerular capillary wall (long arrow) is similar to that of the tubular basement membranes (short arrow), and the mesangial cells and mesangial matrix are located in the central or stalk regions of the tuft (arrows).