Histochoice formulation is a secret but I found out that it is a very dilute
glyoxal (an aldehyde) in proprietary buffers. We buy gallon bottles and
prefilled vials for the endosccopy suite and mix with 20% volume of 95%
alcohol for use. It does not harden tissues like formalin, tissues look raw
longer and the histology of colons that sit in it unopened is inferior with
autolysis. But it works very well when you have the surgeons open specimens
that can't be grossed till the morning. Nuclear detail is very sharp and
special stains look very good. Many antibodies require no antigen retrieval,
cytokeratins, vimentin,  and chromogrannins are BRILLIANT. ER/PR still need
HIER.  I only use formalin now for villous adenomas and other friable
mucosal lesions and difficult colons and total cystectomies that are too
mushy to section thinly with Histochoice. Lymphomas benefit from formalin as
well, the lymphoid cells appear a little shrunken with Histochoice so we put
one or two slices in formalin.No problem putting the formalin fixed stuff on
the Histochoice tissue processor either, they look lovely.  Maybe one
percent of my difficult grosses go into formalin, the routine stuff goes
into Histochoice which we dump down the drain.

Jeff Silverman HT HTL QIHC (ASCP)
Pathologists' Assistant
Southside Hospital
Bay Shore NY USA