[Histonet] Embedding W/WO Melted Paraffin

[Gayle Callis]

>Not frivilous at all. 
>
>I would never put cassettes with tissues IN my embedding center reservoir,
that is asking for the proverbial carryovers! Pieces of tiny tissues can
come out of those cassettes and cross contaminate a new block when paraffin
is dispensed into another samples embedding mold! 
>
>There is no law to say you can't put melted paraffin in the cassette
holding reservoir.  In fact, when doing FDA/GLP, this is exactly what we
did to put a thermometer in that melted paraffin to know reservoir
temperature.  Readout temperatures were not accurate and we were required
to use a certified calibrated thermometer. 
>
>We place cassettes in the dry reservoir all the time (there is always some
melted paraffin in there!) without problems. But that reservoir is set at
60C, the melting point of the paraffin, so if you are experiencing solid
paraffin coming from dry reservoir, readjust the temperature so you samples
stay melted. 
>
>If you use colored cassettes for biopsies, and worried about cooking them,
the color will alert you to embed these biopsies first.  Cooking is the
result of excessive temperature, so make sure the temp is adjusted on all
surfaces of your embedding center, also the paraffin dispenser, and dry
reservoir.   
>
>
>
>At 10:37 PM 1/20/2004 EST, you wrote:
>>Hi, everyone:
>>In order to settle a difference of opinion between generations of trained 
>>Histotechs in my lab, may I have feedback from anyone interested in
responding?
>>Do you cover the blocks in melted paraffin in the embedding centre
reservior 
>>and hold them that way while embedding? or....
>>Do you dump them in the warm reservior "dry" (not covered in melted
paraffin) 
>>and embed them that way?
>>Do you consider this "dry" method as bad technique since a tiny biopsy 
>>specimen MAY not be noticed as the paraffin quickly solidifies?
>>We have a dispute.  I have researched every book I can find and there is no 
>>reference to it anywhere.  A newly trained tech that came to work for us
said 
>>no mention was made during her training period.  Some techs did...and some 
>>didn't. As a tech of nearly 27 years, I find this practice to be just
asking for 
>>trouble.  I was trained to keep everything melted.  There seems to be some 
>>argument against keeping the cassettes in the melted paraffin, claiming
it "cooks" 
>>the biopsies.  I don't buy it, but what are the opinions of others?
>>It seems so basic to me.  I hope this does not come across as frivilous.  
>>Thanks for your input.
>>
>>Dannie Blake HT(ASCP)  Histology Lead Tech
>>Fresno Community Medical Centre
>>Fresno, California
>>
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>>
>>
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology 
Montana State University - Bozeman
PO Box 173610
Bozeman MT 59717-3610
406 994-6367 (lab with voice mail)
406 994-4303 (FAX)