Staining, Histochemistry and Histotechnology
(Frequently Asked Questions)
Dr. John A. Kiernan
Department of Anatomy
and Cell Biology
The University of Western Ontario
Fatty specimens: Processing into paraffin
What is the best way to paraffin-embed specimens that contain a lot of fat?
1. Process by hand, allowing more time and bigger volumes of all solvents than for non-fatty pieces of tissue.
2. Don't put them through an automatic processor because you'll get grease in all the solvents. (If you don't believe this, put a bit of skin in about 10 times its volume of 95% alcohol for an hour, then add some water to the alcohol. Result: a milky emulsion.)
3. Xylene is better than a "xylene substitute."
[Unfortunately I mislaid the sources of these pieces of advice. For what it's worth, I agree strongly with the first two, but lack the experience to comment on the third. J. A. Kiernan. ]