Specimen Collection Guideline

Histology

• For adequate formalin penetration, ensure all biopsy specimens are fixed in a 10:1 ratio of formalin to tissue.
  
  GOOD 10:1 Ratio
  
  
  BAD
  
• If possible, submit the WHOLE specimen. If the specimen size is large eg. whole spleen, make multiple slices 1cm apart (“bread loafing”) before placing in formalin to allow better formalin penetration as formalin does not penetrate greater than 5mm into tissue. The only exception is brain, which can be fixed whole without slicing.
  
• You may wish to ink the surgical margins prior to placement in formalin. Allow the ink to dry before putting into formalin.
• Specimens >5 cubic cms in volume may be fixed in formalin for 48 hours at the clinic and forwarded to the laboratory with a reduced formalin:tissue ratio. This is especially useful for large samples, where several days fixation in large volumes of formalin at the veterinary clinic leads to good tissue fixation. Lower volume of formalin is required when the sample is in transit.
• If accurate identification of individual tissue samples is required, multiple tissue samples should be placed in separate containers or biopsy cassettes that are clearly labelled.
• All samples must be submitted in a leak-proof plastic container. Do not use glass container as they may break during transportation. These containers may be purchased at CityU VDL or elsewhere.