[Histonet] Histonet Digest, Vol 154, Issue 7ubject: fixing fatty skin specimens

Steve McClain SteveM at mcclainlab.com
Sat Sep 10 06:19:34 CDT 2016

Not sure I understand your question.  
But assume you are looking for margins on a re-excision of cancer or melanoma.
Are you using a sufficient -20 times volume of clean 10% nbf? 
And changing it often?
Switch to 20% nbf
Or switch to 100% formaldehyde! True dat- Stanford's Dr. McNeal fixed prostates ~6 hours in 37% raw unbuffered in 1986. (We also used Mercury B5 in 1986)

The question is whether what are you studying (IHC, PCR ) will stand up to additional fixation or post fixation methods treatment.

My plan A approach is to use plenty of  clean 10-20% formalin and change it every 6-24hours. Once it firms up, gross and bread loaf slice and get into 2x3 INCH teabags.
lay those out for another 3-12-24 hours in 70% alcohol, then process teabags for 12-16-18 hours ROOM TEMPs  program 3.

heat fixation- I've seen processor demos where microwave cooked tissues processed well and according to the rep 'cut like butter' but 12 years ago I could not photograph the results.

We've had decent results w 1 hour RT Carnoy's postfixation in some samples. Love this stuff.  It firms up fat, fixes mucin. It can over harden tissue (not in 1hr) and causes shrinkage. But DO NOT HEAT Carnoy's !!! I read it generates phosgene gas. 

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