Re: Penfix. Is it a secret?

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John Kiernan speaks my mind in his response about the use of secret-formula

Pen-Fix is a Richard Allan Scientific product, with the following hype:

>>Pen-Fix is a uniquely buffered alcoholic formalin fixative. It is designed
to perform well with fatty or thick tissue sections. Fixation and dehydration
simultaneously and the penetration rate is 3 times faster than that of 10%
Neutral Buffered Formalin. Pen-Fix is an excellent frozen section fixative
and can be used on all open or closed tissue processors and in the grossing
room. It is recommended for use in the second and/or third stations of the
processor as a secondary fixative.<<

I have used this product on occasion. It has the ethyl acetate ("airplane
dope") odor expected from a mixture of acetic acid and ethanol, and it also
contains formaldehyde. It is thus fairly similar to Davidson's fixative (see
my Web page
for more information on that).

In my experience it does not work as well as Davidson's fixative for clearing
mesenteric fat to look for small lymph nodes in colon cancer resection
specimens - lymph nodes are not as well opacified, and the texture of the fat
makes dissection more difficult. I was also not very impressed with the
quality of the sections, though none of the labs in which I have seen it used
prepares very good slides.

If I ran the zoo, I would prefer to prepare my own Davidson's fixative, and I
suppose it would be cheaper to do so.

Bob Richmond
Samurai Pathologist
Knoxville TN

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