Your veterinarian has many different types of tests that are at his/her disposal in order to make a diagnosis. Most tests, however, are indirect measures of the body’s response to disease. One of the most direct and therefore useful tests that can be performed is a biopsy. A qualified pathologist then examines the tissue that is taken from the area or organ in question under a microscope. This is probably the best means of confirming a tentative diagnosis.
There are several techniques for obtaining a biopsy. A needle biopsy is a method whereby a small core sample is taken for analysis. This method has the advantage of being relatively noninvasive, quick and easy to perform. Needle biopsies are most often applied when the tissue is easy to reach such as with a surface growth. The down side of this method is the small sample size and that it is a ‘blind” procedure which may not be representative of the tissues present. By contrast, the full thickness and wedge biopsy methods are more reliable due to the large volume of cells harvested. These methods, however, require a more invasive operation than the needle biopsies.
Once the biopsy sample has been collected the tissue is placed into a container with a preservative such as formaldehyde. This keeps the cells intact while the specimen is transported to the laboratory. A veterinary pathologist will then take thin slices of the tissue, apply a stain and then evaluate the cells under a microscope. Since most diseases leave a characteristic “foot print” on the cells the pathologist can thereby recognize the disease and make a diagnosis. In addition, information such as the future course of the disease (prognosis), a grading system for malignancies and whether or not the margins of the sample are “clean” or not will be reported. Most laboratories are able to process a biopsy sample within 3-5 days for a reasonable cost.
With the relative safety of todays anesthetics combined with technologically advanced tools, such as the ultrasound and flexible fiberoptic scopes, the risk benefit ratio is clearly in favor of obtaining the biopsy sample. The accuracy of a biopsy as a test is usually good to excellent if the tissue is representative of the problem. Your veterinarian will be able to advise you on when a biopsy is indicated and can often perform the procedure within the hospital on short notice. In most cases the after care is minimal and so is any discomfort.