Matt Lunetta at Longmont United Hospital asks:
>> I am doing a McMannas [sic] PAS with light green on a fungus but am unsure how much of the light green it is to show. Every time I have done this stain so far the light green has been extremely faint. - I have been using a fungus (in lung) as a control. I have been unable to find a photo of what this stain should look like.<<
The PAS stain (McManus, about 1946) when used for fungi is indeed often counterstained with light green SF (or the closely related fast green FCF). The green can be quite faint, as long as you can see the nuclei well enough to orient yourself.
If the green is too dense, it may make the fungi a little hard to see. This color combination can cause problems for the pathologist (one man in eight) who is red-green color-blind.
Trivia time: the "FCF" after fast green supposedly stands for "for coloring food". Like other triarylmethyl dyes, fast green is probably a potent carcinogen. That was a LONG time ago!
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