[Histonet] glyoxal fixation
The people at Anatech, makers of Prefer fixative, have published a review of
glyoxal fixation that every pathologist and histotechnologist ought to read.
This working surgical pathologist would like to add - and solicit - some
comments on Histonet.
"Glyoxal Fixation and Its Relationship to Immunohistochemistry". Richard W.
Dapson, Ada T. Feldman, and Dee Wolfe. Anatech Limited, Battle Creek MI. The
Journal of Histotechnology June 2006;29:65-76.
I don't want to change, but I think we all need to be prepared for the day
when a manager walks into our laboratory, or a letter from a regulatory agency
arrives in the mail, telling us that we have to get rid of formaldehyde right
now. Probably glyoxal is the only acceptable substitute, and we all need to
have a look at it. I have a number of questions.
Interchangeability of glyoxal products: Prefer is described as a buffered
solution of glyoxal with a pH of about 4. The formula is a trade secret.
Competing glyoxal products probably also have trade-secret formulas. So can a lab
change brands of buffered glyoxal without problems, or does it have to stay with a
particular brand with its trade-secret buffering? - We've seen a similar
problem with distilling aliphatic xylene substitutes: every one of them requires a
separate distillation routine, at least on a spinning-band still. - I'll
leave it to John Kiernan to comment on the appropriateness of trade-secret
reagents in histopathology.
Limited time in the fixative: Tissue can be left in neutral buffered formalin
for quite a long time and still be stainable, but tissue stored in glyoxal
becomes unstainable after about two weeks. Can glyoxal fixed tissue be
transferred to 70% ethanol for more prolonged storage? - A very occasional surgical
specimen requires additional blocks after a week - a bigger problem will be the
pathologist who doesn't trim his autopsies promptly.
Transition period: A laboratory changing to glyoxal would have to keep IHC
procedures for both fixatives working for some time. There would have to be some
way to identify whether a block was fixed in formaldehyde or glyoxal.
Eosinophilia: One ought to be able to distinguish eosinophils from
neutrophils in tissue sections by nuclear morphology, without having to see granules.
But quantitation of eosinophils - needed in an increasing number of GI biopsy
situations - could be a problem. We might need an IHC for eosinophils in some of
Lysis of erythrocytes: Not much of a problem, since we're used to it with
acid fixatives anyway.
Breast cancer: Elimination of nuclear bubble artifact in breast biopsy
specimens may raise the apparent nuclear grade of tumors, and thus increase
Nottingham (Elston-Ellis) scores.
Prostate biopsies: I'd want to see some prostate biopsies - is somebody from
OURLab in Nashville still on this list? - with formaldehyde fixation, nucleoli
are a strong criterion of malignancy, and if glyoxal fixation demonstrates
nucleoli in benign ductal epithelium, this criterion is lost.
Knoxville TN and Gastonia NC
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