[Histonet] Congo red

[Lee & Peggy Wenk]

Is it ONE particular case that is giving you problems, or ALL cases of 
amyloid? Maybe just the control?

If the amyloid is a large deposit, that has been in the patient for a long 
time, the beta pleats can get warped, and the Congo red will be very pale to 
no staining. In those cases, we:
- Use the Auramine-Rhodamine fluorescence scope (hit slide with green light) 
on the Congo red stained tissue. Congo red amyloid will fluoresce orange 
against a black background.
- Do a crystal violet stain. Amyloid will be pink violet against a blue 
purple background.
- Do a Thioflavin T stain. Use the FITC fluorescence microscope (hit slide 
with blue light). TFT will fluoresce yellow against a black background.

All the amyloid stains have a weakness when it comes to staining amyloid. 
There isn't one that works all the time. If the Congo red is working fine, 
then that's the only stain we do. But if the Congo red isn't staining 
correctly (our control is great, but the patient's tissue is weak to no 
staining), then we do one or more of the above options.

If you need the crystal violet or TFT procedure, let me know.

Peggy A. Wenk, HTL(ASCP)SLS
Beaumont Hospital
Royal Oak, MI 48073
The opinions expressed are mine, and do not reflect those of my employer.

-----Original Message----- 
From: Bryan Llewellyn
Sent: Thursday, March 01, 2012 12:22 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Congo red

Bennhold's method is not the easiest to give good results. Try
Highmans's method
(http://stainsfile.info/StainsFile/stain/amyloid/congohighman.htm). It
is much easier to control.

Remember that congo red is not an intensely coloured dye and the results
are often pale. If your pathologists want a punchier stain try sirius
red F3B (NOT 4B), as this is a deeper red than congo red. It can be used
in a Highman type procedure as a direct substitute for congo red. It
also gives green birefringence, again somewhat darker than congo red.

Bryan Llewellyn



Cheri Miller wrote:
> Anyone have any solution to a week Congo Red? I use Rowley  Congo red, 1% 
> aqueous order # S0-496. our procedure is Benholds and I cut at 5-6 
> microns. And I leave in the solution for up to 4 hours and the paths are 
> still saying it is weak. Any ideas? I have even stopped the Alkaline 
> alcohol differentiation step and its still too weak.
>
> Cheryl A. Miller HT(ASCP)cm
> Histology/Cytology Prep Supervisor
> Physicians Laboratory Services
> Omaha, NE. 402 731 4145 ext. 554
>
>
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