Animal Reference Pathology

525 East 4500 South Suite F200
Salt Lake City, UT 84107

(180)042-6209 x9


Tissues from the body taken for diagnosis of disease processes by pathologists must be handled, identified and transported in a manner that will give the best end product for the pathologist to evaluate.  The following guidelines may prove helpful in this important process.


Tissue Fixation

Fixation, which preserves tissue structure and chemical composition in a state as close as possible to the living condition, is the most important step in the preparation of tissue for microscopic examination.

  • A minimum of a 10:1 ratio (10% neutral buffered formalin to tissue) should be used to fix the tissue.
  • Formalin penetrates tissue at the rate of 1 mm per hour or less, particularly if the tissue is thick.  The diffusion rate slows, the deeper into the tissue it penetrates.  Plan accordingly.
  • Certain large specimens should be sectioned or opened up to allow for more complete formalin penetration to help prevent autolysis in the center of the tissue examined.  When opening up large cutaneous tissues and evaluation of deep surgical margins is desired, care should be taken to not disrupt the deep tissue structure. Eyes should not be opened up or sectioned.
    Please feel free to call and speak with one of our pathologists if you are concerned about where to cut.
  • Mix, swirl or agitate the solution so that all surface areas of the tissue are exposed to the formalin.
  • For large tissue specimens, consider replenishing or replacing the formalin during the fixing process.  Formalin loses potency over a long period of time, so keeping it replenished enhances penetration and fixation rate.


Tissue Identification and Transport

  • Federal shipping regulations must be observed when transporting laboratory specimens via any Express or Ground delivery service, such as the carrier we use, FedEx. Our biopsy shipping containers/mailers comply with DOT shipping regulations.  These regulations stipulate that biopsy specimens should be put into a primary container that is leak resistant.  The primary container must be put into a secondary leak resistant container and between the primary and secondary containers, there should be enough absorbent material to absorb all the liquid contained in the primary container.  The secondary container should then be placed into a sturdy, rigid-walled outer container for shipping.  This outer container can then be put inside a Clinical Pak (FedEx product) bag for shipping.  Or, if the outer container is too large to fit into a Clinical Pak, an address label such as an airbill can be placed directly onto the outer container.
  • Always fill out the test request form as completely as possible including account number and name, patient identification, lesion or process description, history, duration, site(s), pathologist preference if desired and working clinical diagnosis.  The more we know about the case, the more complete our results will be.
  • We provide species specific test request forms.  We also provide a request form specific to oral tumors and lesions.  These forms can be found on our website by clicking HERE or you can contact customer support at 800-426-2099 if you have questions about our test request forms.  It is always advisable to keep a copy of the test request form when submitting biopsies to us.
  • When submitting multiple specimens/sites from the same patient, fill out only 1 test request form, but indicate on the form how many bottles or sites there was for that patient and label the bottles, such as 1 of 3, 2 of 3 and 3 of 3.  Or if submitting multiple sites in one container and you want them identified on the report, use sutures or some other identification on the tissues and the requisition form.
  • Animal Reference Pathology provides formalin containers and mailers along with FedEx Express airbills and Clinical Pak bags at no charge.  We also supply histology cassettes for submission of GI or small internal organ tissues.  We pay for shipping when specimens are submitted in our containers.  For oversized packages, containers that leak or that are difficult to work with, such as some pill bottles and bottles with narrow necks, there may be a surcharge applied.  When requesting more supplies, plan ahead if possible.  Allow up to 2 weeks for delivery of supplies.  NOTE:  Do not use glass, polystyrene, narrow-necked or other containers that may break, shatter or make it difficult to extract the tissue specimens.  Do not use butter tubs, Tupperware type containers or other containers that are not leak resistant.  At higher elevations, such as in flight, these containers are very susceptible to leakage.  Do not tape or use parafilm to help seal the lid.  Tape will not seal a container that is prone to leak, it only creates a bigger mess on arrival at the lab.


Remember, the shipper is responsible for the proper packing and shipping of specimens to the lab and is therefore liable for any damages that may occur from improperly packaged shipments.