Reverse processing by hand after processor failure

From:Gayle Callis

Melt paraffin from around tissue in block, return tissue to a cassette.   I
would do this by hand! not in my processor. Purge cycle has too much heat
involved, I agree with Fred on this point! 

Xylene X 2 changes 1 hour each - using agitation helps, I would avoid heat!
No need to cook tissues twice.  
100% X 2 changes 1 hour each
95% X 2 changes 1 hour each at this point, you may choose to reprocess
(explanation below)
70% X 2 changes 1 hour  

I don't think fixation needs repeating, that first station or two of
fixative can be avoided. If a tissue is not completely fixed before going
into alcohols then alcohols probably complete fixation anyway, even during

If you get all the way to 70%, reprocess back into paraffin.  If tissue was
totally fixed to begin with, but is just poorly dehydrated (you dehydrated
then rehydrated with your incorrect lineup of solvents) - you can go back
to one change of 95% alcohol to remove residual water, then reprocess to
paraffin. This will save time.  

It may not be ideal but tissue is usually recovered enough to cut, stain
and make diagnosis, IHC may be a problem.  

Gayle Callis
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
S. 19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (lab with voice mail)
406 994-4303 (FAX)


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