Cryotomy or frozen sectioning allows the preservation and demonstration of tissue substances that are either lost or affected by routine paraffin processing (e.g., lipid, enzymic or immunoreactive sites). Samples may be fixed or collected fresh at necropsy. Fixed samples may be transferred to a sucrose solution prior to sectioning to prevent water crystallization. Unfixed samples may be snap frozen and stored.
Tissues are routinely embedded in a viscous media, sectioned on a cryostat and mounted on to glass slides. The most common stain requested is the Oil Red O to demonstrate the cellular lipid content.