[Histonet] Processing animal fat

[Ann Lowder]

Peggy,

I have worked both with animal tissue and human tissue, though never with pig specifically.  I do, however, imagine that the pig specimens are extremely fatty much like human breast tissue.  The very thick breast specimens that sometimes do not process completely have the same appearance as you have described with the crumbly white areas.  I do not know how much time you have to process your specimens or what your workflow is like; however, the really fatty tissue I have seen seems to section better when the processing schedule is longer (but you do have to make sure not to overprocess the tissue either if the skin is still attached as it can harden).  The hardest part is finding the medium where you have correctly processed the fat without overdoing the skin.  Currently our very fatty breast specimens are processed overnight on a 12 hour process, but I have seen excellent processing even with a 14 hour process if they are very thick specimens (keep in mind this is on an old machine so this could be shortened possibly with something like a Polaris).  Enough time in formalin is definitely required as it takes a while for anything to penetrate the fatty cells, but our protocol also ends with extended time in paraffin under vacuum.  I think the important part about the paraffin or other stations with the extended processing time means that the processor cycles the reagents more times.  It also would depend on if you are microwave processing or using a vacuum processor, but if some came out ok after an hour, maybe including a formalin vacuum station and additional paraffin under vacuum at the end?  Are your reagents heated or are you able to include heat while they are processing?  We get really excellent feedback from our pathologists about the sections from this process, so I hope some of this info helps.  

Ann Lowder, HT (ASCP)
aelowder <@t> novanthealth.org or ael <@t> unc.edu 

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu
[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Sherwood,
Margaret 
Sent: Thursday, March 17, 2011 2:57 PM
To: histonet <@t> lists.utsouthwestern.edu
Subject: Re: [Histonet] Processing animal fat

My question is directed specifically to veterinary histologists or histologists
who also do a fair amount of animal processing.  We are having a terrible time
processing pig fat.  We had problems previously, but thought we had solved them.
This latest project (pig skin with a lot of fat attached) came out awful.  The
fat was not adequately processed:  couldn't section it, it just crumbled.  In
the block, it appears white and crumbly.  The funny thing is some blocks came
out all right, but most didn't.

PLEASE help!  Let me know how you process your animal fat (sp. Pig)! Is there a
size issue (we trim it if it is greater than 5mm)?  We have gotten help from the
histonet before and instituted these suggestions (i.e. let sit in formalin for
48 hours; put in cassettes in a 60 degree oven for 1-2 hours and then cool to
room temp. Then process using a 1 hour program).

Any help would be appreciated.

Thanks!
Peggy

Peggy Sherwood
Lab Associate, Photopathology
Wellman Center for Photomedicine (EDR 214)
Massachusetts General Hospital
55 Fruit Street
Boston, MA 02114-2696
617-724-4839 (voice mail)
617-726-6983 (lab)
617-726-1206 (fax)
msherwood <@t> partners.org 




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