The Biopsy

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Clinical Oncology Service
Veterinary Hospital of the University of Pennsylvania (VHUP)
Last Modified: November 1, 2001

A biopsy is the surgical removal of a piece of tissue from your animal, and is recommended by your veterinarian in order to establish a tissue diagnosis. The diagnosis is determined by the examination of this tissue under a microscope by a pathologist. Microscopic evaluation of the tissue(s) allows the pathologist to determine whether the tissue is inflammatory, infectious, or cancerous. If the tissue is cancerous, the biopsy provides important information regarding the type and nature of the cancer. In some cases, a biopsy specimen can be useful to evaluate whether a tumor has been completely removed ("clean" margins) or whether some tumor cells have been left behind ("dirty" margins).

The biopsy specimen may be a representative piece of an abnormal tissue (incisional biopsy) or may be a large piece of tissue including the entire diseased area (excisional biopsy). It is the judgement of the clinician whether the biopsy specimen should be excisional or incisional.

Once the tissue is removed it is immersed in a 10% formalin solution for fixation. Fixation is a method of preserving the material and prevents decomposition. Once the tissue is received by a pathology laboratory, representative samples are processed, the microscopic slides prepared, and the slides evaluated by the pathologist. The pathologist will then provide a final report to the referring clinician.

In most cases a report will be available in three working days. However, in some instances this may take longer. These include:


  • Bone biopsies which need to be softened prior to processing.



  • Special staining techniques that may be required to identify cells, cell products, bacteria,fungi, etc.


  • Difficult or unusual cases for which the pathologist will seek a consultation with other pathologists.


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