Cryosections

Cryosections are thin slices of biological tissue prepared by rapid freezing rather than fixed and embedded in paraffin. They are typically cut in a cryostat at temperatures around -20 to -30°C and mounted on glass slides. Tissue is often preserved in a water-soluble embedding medium such as optimum cutting temperature compound (OCT) to support thin sectioning. Section thickness commonly ranges from 5 to 15 micrometers.

Preparation involves quickly freezing fresh tissue, often by immersion in isopentane cooled with liquid nitrogen, followed by embedding in OCT and mounting on a cryostat chuck. The material is then sectioned with a microtome inside the cryostat. Sections are collected on slides and may be fixed briefly with cold solvents such as acetone or methanol, or used unfixed depending on the intended analysis. They can be stained with standard histological dyes or subjected to immunohistochemical or immunofluorescent labeling, in situ hybridization, or enzyme histochemistry.

Cryosections are used for rapid diagnostic purposes, particularly intraoperative consultations where quick histological assessment is needed. They are also valuable in research contexts where preservation of antigenicity, enzymatic activity, or nucleic acids is important, enabling flexible panel choices for staining and imaging.

Advantages of cryosections include fast turnaround, improved preservation of certain epitopes and enzymes, and suitability for multiple downstream analyses on fresh or lightly processed tissue. Limitations include potential ice crystal–related artifacts, generally poorer morphological detail compared with paraffin sections, and the need for specialized equipment and expertise. Freeze-thaw stability is variable, so storage conditions are important, typically at -80°C for short or long-term storage.