Special Stain Series, Part 1: Gomori Methenamine Silver
The Gomori stain is a visually interesting one with several applications. When used in conjunction with silver nitrate it is mainly used to demonstrate urates in tissue but will stain other substances such as mucin and pathogenic fungi. I was able to do two slides with the automatic special stainer in the lab, one positive control slide (fig. 1) and one section of small bowel (fig. 2), both at 60x high dry magnification plus a slight amount of zoom from my phone (which I used in order to take the pictures):
Figure 1: Positive control demonstrating fungi on lung (maybe? see hemming and hawing below for more details).
Before we discuss mechanisms and diagnostic value, it’s worth saying that I’m not 100% certain what the control tissue is. The general pulled-cotton look to it makes me suspect it’s lung, which would make some sense for certain fungal infections (psittacosis, anyone?) but I can certainly be wrong about that. I’m not strong on microanatomy and my program doesn’t focus on it too much which sucks so I can’t identify just by eyeballing it.The way this project was organized had me looking up the correct control slide from a box of non-accessioned (ie not identified by a patient number & entirely divorced from case history) tissues which the pathologist passed onto us for the explicit purpose of acting as a positive control in future patient cases. When I asked my instructor what sort of tissue it was she just said fungi and urates can show up anywhere in the body, which like, yeah. But. That’s not what I asked…
Anyhow. The Gomori stain was developed by Hungarian-american physician and famous histochemist George Gomori in 1950. The Gomori methenamine silver method (’GMS’) is generally used to demonstrate urate crystals in tissue, which will be present in patients with gout. Here we see it staining fungi in the control and what I assume to be mucin within intestinal glands in small bowel (dark gray and light gray, respectively). This is a good time to remember that silver stains are pretty non-specific; in this case, silver nitrate just want to glom onto something and get reduced into to its visible form, and it’s not picky about what it interacts with. Heck, spill some silver nitrate on your skin and it’ll react with you and you’ll get some sweet new science freckles. Don’t actually that’s very dangerous.