ALT MINIMAL CHANGE DISEASE: Low-power view of the kidney, showing no detectable histologic abnormalities. (Hematoxylin and eosin [H&E] stain)

ALT MINIMAL CHANGE DISEASE: By electron microscopy, there is extensive foot process effacement (or fusion), with hypertrophy of the podocyte cell bodies. The primary processes are intact and form slender cytoplasmic extensions from the cell bodies to the foot processes. The glomerular basement membranes appear normal in thickness, without electron-dense deposits.

ALT DIFFUSE DIABETIC GLOMERULOSCLEROSIS: There is global widening of the glomerular mesangial regions. Moderate to marked enlargement of the glomeruli may be visible. These changes in this glomerulus are representative of the changes in all glomeruli, thus the term “diffuse” glomerulosclerosis. There is also accompanying arteriolosclerosis. (Periodic acid–Schiff [PAS] stain)

ALT DIFFUSE DIABETIC GLOMERULOSCLEROSIS: There is widening of the glomerular mesangial regions and, often, associated diffuse mild thickening of the glomerular basement membranes. The mild to moderately thickened glomerular basement membranes cannot be discerned as thickened in a thin light microscopic section at this stage. In this photomicrograph, there is glomerular capillary ectasia and enlargement of some of the visceral epithelial cells, suggesting proteinuria. (Jones methenamine silver [JMS] stain)

ALT NODULAR DIABETIC GLOMERULOSCLEROSIS: A number of rounded, acellular mesangial nodules (Kimmelstiel-Wilson nodules) are present in the glomerular mesangial regions. They vary in size. Most of the cellularity is noted at the edges of the nodules. (PAS stain)

ALT NODULAR DIABETIC GLOMERULOSCLEROSIS: Several large Kimmelstiel-Wilson mesangial nodules are present throughout this glomerular tuft. (JMS stain)

ALT SEMINOMA Left: A dense lymphocytic infiltrate is centered on fibrous septa. Right: This seminoma shows separate, discontinuous nodules; variably prominent fibrous bands are in the largest nodule.

ALT PURE RED CELL APLASIA: Bone marrow aspirate showing a lack of nucleated RBCs (A). Bone marrow sections showing a lack of erythroid islands on H&E stains (B,C). Erythroid precursors are absent on a CD71 stain (D).

ALT NORMAL CHOROID PLEXUS: The regular cell spacing and hobnail appearance of normal choroid plexus distinguishes it from choroid plexus papilloma.