[Histonet] Processing animal fat

[Reilly, Laurie]

Dear Margaret and fellow histonetters,

The major problem with processing fatty tissues, assuming that they are fixed properly, is that Ethanol is not a good solvent for fat and therefore connot penetrate the tissues completely, so the tissues are inadequately dehydrated.
We have had some success with lipomas by adding a "degreasing" step of xylene into the processing schedule.
70% ethanol
80% ethanol
90% ethanol
95% ethanol
Absolute ethanol
Xylene
Absolute ethanol
Xylene
Xylene
Paraffin
Paraffin
Paraffin
The first Absolute ethanol will dehydrate the tissue to some extent. The next Xylene step will remove most of the fat and then the second Absolute ethanol can complete the dehydration.

A compromise situation that we use routinely is to have Absolute ethanol, 50:50 Absolute ethanol:Xylene, Xylene This is not quite as effective but it is less disruptive to the normal schedule and handles moderately fatty tissues.

            Regards from Townsville, Australia.
                      Laurie.

Mr. Laurie REILLY
Histopathology
School of  Veterinary and Biomedical Sciences
James Cook University
Townsville  Qld.  4811
Australia.

Phone 07 4781 4468

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Sherwood, Margaret 
Sent: Friday, 18 March 2011 5:57 AM
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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