Pathology and Histopathology

Whole Animal submissions

Whole animals submitted for necropsy should not be frozen, but should be shipped overnight on ice within an insulated container. Frozen carcasses may take a long time to thaw and greatly increase turn-around time. Freezing also kills many bacteria, often preventing accurate bacterial culture, and creates serious tissue artifacts on histopathology.

By submitting diagnostic specimens, clients understand that such specimens will not be returned to them unless prior arrangements are made with the lab. In the special case of carcasses submitted for necropsy: remains will only be released to registered pet cremation services, to prevent accidental transmission of any potential pathogens from the laboratory; animal remains designated as "hold for cremation service" will be held for a maximum of two (2) weeks, after which the Laboratory will dispose of them en masse with other carcasses.

Histopathology Specimen submissions

Specimens for histopathology should be submitted in neutral buffered 10% formalin solution in wide-mouthed, leak- and shatter-proof containers. The volume ratio of tissue to formalin must be at least 1:10. Tissues fixed for 24 hours in an appropriate amount of formalin prior to submission may be subsequently submitted in a smaller container with a reduced amount of fixative, thus decreasing the size and weight of the container used for shipping. Containers must be labeled with names of the veterinarian, owner, and animal. The label must also have the date collected and information about the sample submitted. Pencil should be used if there is a chance that the label will come in contact with formalin. When multiple biopsies are submitted with one case, each tissue should be submitted in a separate container and labeled appropriately. For neoplasms, inking of surgical margins with India ink, for example, is recommended for the most accurate assessment of completeness of excision.

Improper Handling

Improper handling or fixation of tissues can induce artifacts that may result in non-diagnostic specimens. Examples of improper handling include:

  • Failure to place tissues in formalin immediately after collection
    Unfixed specimens are subject to dehydration, autolysis, and proliferation of saprophytic bacteria. Refrigeration slows, but does not prevent these changes.
  • Inadequate fixation
    Using an inadequate volume of fixative, or attempting to fix large specimens (whole kidney,large mass), will result in incomplete fixation and autolysis. Processing is then delayed because unfixed tissues must be placed in a larger container with fresh formalin for additional fixation prior to routine processing. Formalin penetrates tissue at roughly 18 mm per day, and the rate of penetration slows with the thickness of the tissue. It takes approximately 100 hours (4+ days) for formalin to penetrate 36 mm.
  • Improper fixatives
    Alcohol, disinfectants, and saline are unsuitable for transport or fixation of specimens for histopathology and usually result in non-diagnostic samples.
  • Thermal dehydration
    Electrocautery and laser surgery cooks tissues and may destroy small tumors and skin biopsies. A scalpel or punch should be used instead. It is helpful to include the means of collection on the submission form.
  • Chemical dehydration
    Disinfectants and medications applied to the skin or residues on instruments that are chemically sterilized may damage tissues.
  • Freezing
    Ice formation in or around cells causes cell lysis and disrupts normal tissue architecture, resulting in non-diagnostic samples. Additionally, autolysis may occur during thawing.
  • Excessive Pressure
    Excessive pressure from forceps or digits can rupture and/or compress cells (e.g., crush artifact), making them unidentifiable. Small pieces of tissue, such as skin punch biopsies, can be manipulated with a needle rather than forceps to prevent crush artifact.

Skin biopsies for dermatopathology (skin conditions affecting more than one area)

Punch biopsies, at least 6mm in size, of multiple affected areas are recommended. There is a single charge for dermatophology cases, regardless of the number of punch biopsies submitted. We encourage the submission of at least 4-6 skin punch biopsies with primary dermatological disease. Primary lesions are most diagnostic, so biopsy early lesions (e.g., papules, pustules, vesicles, bullae, wheals, etc) rather than chronic ones. Ulcerated lesions are typically not rewarding.

If you are unsure how to most appropriately sample a lesion, please call with questions prior to biopsy.

Report types

Brief/routine report

This report includes diagnosis and comment. All information required for prognosis (e.g. mitotic rate, completeness of excision, vascular invasion, behavior of lesions, etc.) is included in the comment.

Extended report

This report includes the information in the brief/routine report, as well as a detailed histologic description of the lesion.

FFT (formalin fixed and fresh tissue/practitioner necropsy)

Submission of a complete set of tissues is recommended. Both formalin-fixed and fresh tissues should be submitted. Alternatively, fresh tissues may be saved, refrigerated, or frozen, if microbial culture or toxicological testing is not needed. Definitive diagnosis of infectious diseases and toxins often requires ancillary testing (i.e., culture, virus isolation, fluorescent antibody testing, electron microscopy, etc.) that cannot be performed on formalin-fixed tissues.

The following is a list of suggested tissues to be collected during practitioner necropsies:

  1. Brain and/or spinal cord
  2. Heart
  3. Lungs
  4. Liver
  5. Spleen
  6. Kidney
  7. Stomach
  8. Small intestine
  9. Large intestine
  10. Lymph nodes
  11. Urinary bladder
  12. Thymus on young animals
  13. Bone marrow
  14. Skeletal muscle
  15. Adrenal glands
  16. Any affected tissues based on history, clinical signs, and/or gross findings not listed above suchas thyroid gland, reproductive organs, etc.