I have run into this on a few occasions.  It is in the nature of amyloid to
be variable in staining.  If you really must prove its presence, then cut
some of the tissue out of the block, dewax it and send it for EM.  Although
the ultrastructural morphology will be the pits, the very characteristic
structure of amyloid is retained.  We did this on a case a few years ago,
when the only stain that demonstrated it was thioflavin T.  It did turn out
to be amyloid.

Bryan Llewellyn



-----Original Message-----
From: Rick Strogen <strogen@warwick.net>
To: HistoNet@Pathology.swmed.edu <HistoNet@Pathology.swmed.edu>
Date: October 8, 1998 6:15 PM
Subject: congo red


>One of our pathologists wanted me to post this question:
>We have a spleen that is amyloid positive and crystal violet positive.
>Our Congo Red is negative.  All reagents are new and the control is also
>either negative or weak staining.  Does anyone out there have any ideas
>or help in this matter?
>
>Robin Strogen
>The Valley Hospital
>Ridgewood, NJ
>
>