HIS Frozen Sections Flashcards
What is the CAP accreditation standard time for cryotomy?
20 minutes
4 major applications of cryotomy
- Intra-operative consultations
- Enzyme histochemistry
- Immunofluorescent techniques
- Lipid stains
Cryotomy in intra-operative consultations
during surgery, physician can request Histo lab to identify an unexpected finding or confirm that a biopsy margin is negative for cancer before closing the patient
Enzyme histochemistry in cryotomy
Freezing tissue prevents:
1. Degradation after being removed from blood supply
2. Enzyme activity being reduced from chemical fixation
Immunofluorescent techniques in cryotomy
- Labile antigens are preserved from being denatured by chemical fixation
- Antibodies with fluorescent labels can be used
Lipid stains in cryotomy
- Preserves lipids that would be removed by solvents in tissue processing
- Neutral lipids (fat) can be visualized
Describe procedure of cyrotomy
- Rapid freezing of tissue
- Typically set cryostat at -20°C
- Freeze tissue on FSC
- Cut sections one by one onto slides
- Fix briefly in formalin* or alcohol
- Leave to dry or rinse in water immediately before staining
- Intra-operative = stain with H&E or Diff-Quik (commericial Romanowsky stain)
- After pathologist permission, tissue is thawed and fixed in formalin
- After overnight processing, tissue is cut and compared to frozen section
How can freezing artefact be minimized ?
- Freeze tissue as rapidly as possible = smaller crystals
- Use heat extractors, dry ice, or isopentane cooled with liquid nitrogen
Cryostat temp for highly cellular tissue
Warmer temps (-10 to -15°C)
Cryostat temp for open and connective tissue (including adipose)
Colder temps (-20 to -30°C)
T or F: Sections are cut one at a time, rather than forming a ribbon
TRUE; Sections are cut one at a time, rather than forming a ribbon
Intra-operative tissues are stained using…
H&E or Diff-Quik (commercial Romanowsky dye)
Why must frozen sections be compared with thawed sections the following day ?
Frozen (fresh) sections are inferior in quality compared to fixed tissue
Why must PPE be worn when using a cryostat ? (N95, mask, gloves, goggles, gown)
Frozen tissue has not been processed with fixatives/ solvents = potentially infectious
Tissue Chattering
- Regular pattern of horizontal lines = “Venetian blind”
- Tissue/ block is too cold
- Cryotome component is loose
Troubleshoot Tissue Chattering
- warm surface of block directly
- tighten all levers and clamps of cryotome
Tissue Shattering
cryostat temperature is too cold
Shattering is common in which tissue ?
Lymph nodes
Troubleshoot Tissue Shattering
Use heat from gloved thumb to quickly soften the surface of block
Tissue Compression
- section becomes smaller than face of block bc tissue collapsed onto edge of bade when cutting
- block is too warm
- blade is dull
Troubleshoot Tissue Compression
- re-cool block on ice
- use a new blade
Tissue Scores
- vertical lines (PERPENDICULAR to blade) on section
- due to blade defect OR calcification on block
Troubleshoot Scores
- reposition/ use a new blade
- if scores persist = tissue is calcified = inform pathologist
Why would tissue debris float around in the cryostat ? How is this corrected ?
Due to static electricity
- Humidify room or wipe down interior with alcohol
Describe End-of-day Cryostat maintenance
- disinfect with 70% alcohol at end of day
- ensure automatic defrost cycle is turned on
Describe periodic cryostat maintenace
- Defrost and decontaminate using Oxivir/ CaviCide
- UV-light disinfection
- Automatic defrost cycles
- Vacuum cooling coils on the back/ sides of cryostat
