[Histonet] Re: oops - samples directly to paraffin

Monfils, Paul PMonfils <@t> Lifespan.org
Tue Nov 21 12:27:36 CST 2006

Well, that's pretty bad. Not as bad as the time the heating unit on our
processing chamber malfunctioned, and melted all the cassettes into one
bubbling stew of liquified plastic and tissue bits.  But still, bad enough.
HOPEFULLY the tissue samples were well fixed before they were put on the
processor?  If they were unfixed tissues that were intended to go through
fixative on the processor, but went directly into paraffin instead, then I
don't have much hope for them, either in terms of IHC or morphology.  But
well fixed tissue can withstand a lot of abuse and still come out decent. I
would not melt the paraffin if possible. There is too much danger of
dessicating the small tissue samples with heat (some of this may already
have occurred while they were in liquid paraffin). I would try to remove as
much paraffin as possible manually. The paraffin has not infiltrated into
the tissue, since the tissue samples were in aqueous medium immediately
before going into the paraffin. You may find that the cassettes come loose
from the paraffin fairly easily once you break some of the paraffin away.
Actually, refrigerating the beaker for a while may facilitate this process.
Also, if you open a cassette you will probably find that you don't have to
"chip" the tissue out of the paraffin. There should be no bonding of the wax
to the tissue, and any piece of tissue that is exposed can probably be
lifted out of the paraffin easily with forceps, and placed into a new
cassette.  If it appears that you have gotten rid of almost all the paraffin
manually, then I would just put the samples, in new cassettes, back on the
processor, and process as usual.  If you are not able to pick off most of
the paraffin, then it will be necessary to dissolve the remaining paraffin
with your xylene substitute. After that, I would put them on the processor
directly from the xylene substitute, and process as usual.  The alcohols
will remove both the water and the residual xylene substitute from the
tissues, and hopefully they will then infiltrate properly. Good luck! Let us
know how you make out.

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