Extracellular matrix proteins are generally silver positive, resulting in an increase in mesangial argyrophilia (Figures 3 and 4).
Following the algorithm on the left side, this manuscript will initially discuss conditions characterized by an increase in mesangial matrix (increased staining of the mesangium with the silver stain), followed by those on the right side (decreased mesangial argyrophilia).
The light microscopic findings of this condition are very nonspecific, with an increase in mesangial matrix, which results in enhanced argyrophilia (Figures 8 and 9) and occasional thickening of peripheral capillary walls.
The expanded mesangium displays increased argyrophilia. Demonstration of collagen III in the expanded mesangial areas is imperative to confirm the diagnosis.
(26,27) In this condition, silver methenamine stain is most commonly negative, which suggests that the composition of the fibrils determines the degree of argyrophilia.
(4,13) A corollary of the above is that in the early stages, it may be difficult to appreciate a decrease in mesangial argyrophilia because of the focal and mild matrix replacement that may be present.
(44) The end result is that the normal mesangium is replaced by amyloid, explaining the absence of mesangial argyrophilia in the advanced stages of glomerular amyloidosis.