Frozen section - Freezing tissue

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Frozen section

Freezing tissue

Author: Jessica Wallace (see Reviewers page)
Revised: 11 October 2011, last major update October 2011
Copyright: (c) 2011, PathologyOutlines.com, Inc.

Freezing methods
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● Note: most are used in conjunction with heat sinks

● Histobath: being phased-out
● Cryowells: useful in keeping all tissue on an even plane; also helpful in eliminating loss of smaller tissues that are frozen with larger ones, although recommended to not freeze different sizes together
● Aerosol sprays: often canned CO2 (but may aerosolize infectious diseases)
● Liquid nitrogen
● Isopentane based workflow (Virchows Arch 2008;452:305)

Procedure
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● OCT (Optimal Cutting Temperature) or similar embedding media like TBS or Cryogel should be placed on an appropriate sized chuck that has been pre-cooled in a cryostat
● The chuck should be clean
● A toothbrush is useful to remove tissue and OCT
● Dipping the chuck in methanol removes ice crystals
● Place the chuck into a -20 to -15 degree (optimal) cryostat; note that the OCT media should not be frozen completely
● It is better to have a semi-solid consistency; this will alleviate tissue artifact
● Tissue size should be no greater than 3mm-5mm in greatest dimension (thinner specimens have shorter freezing time and minimal ice crystal artifact formation)
● The smaller the tissue, the more even and thorough the freeze
● Place the tissue on the semi-solid chuck and add more media rapidly over the tissue, covering it entirely, but avoiding overflow
● Place chuck quickly back into the cryostat
● Apply heat sink or CO₂ aerosol (optional) to rapidly freeze, or use “quick freeze” option on cryostat

Videos
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Embedding small specimens, Speed embedding

End of Frozen section > Freezing tissue

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