Dog And Cat Biopsy


It’s a scary word, isn’t it?

But it doesn’t have to be, because a biopsy can just as easily bring good news as bad.

First, let’s define biopsy: “The removal and examination of tissue, cells or fluid from the living body.”

So, though we may usually think of a biopsy in terms of taking all or part of a solid tumor, there are other forms of biopsy as well.


One of the least-invasive and best-tolerated procedures to help diagnose a condition in a patient involving a mass, swelling or fluid collection is the Fine Needle Aspirate. To perform it, your pet’s doctor will usually use a big syringe with a small needle. After clipping the hair from the area to be biopsied, and preparing it as one would for surgery, a tiny needle is inserted into the suspicious area, a big vacuum is pulled with a big syringe. If everything goes right, fluid or cells enter the needle (and the syringe, too, if there’s enough of it and it’s free-flowing). The material is now spread on a microscope slide so that the clinician can send it to a pathologist. The pathologist will stain the slide with special stains that allow him to see the details of the cells/fluid/material in hopes of making a diagnosis.

Potential drawbacks of the fine needle aspirate are:

  • a growth may consist of a cell type that doesn’t exfoliate or “give up” cells easily. Therefore the material removed may not contain diagnostic characteristics.
  • because the needle is entering a very small part of a bigger problem area, a tiny needle may miss the most important information. For example, some cancerous tumors may have normal tissue inside them. If the needle happens to enter normal tissue, even though it’s immediately adjacent to cancerous tissue, the result may be a misdiagnosis of normalcy.

That said, a fine needle aspirate is easy, inexpensive and relatively painless. If it gives the practitioner the answers he seeks, it’s great. If it doesn’t, it is still easy to go further to more aggressive biopsies.


Tissue biopsy is usually thought of as removing the entirety of a mass and submitting it to a pathologist for study. In some cases the mass may be too large to remove completely, and a portion is submitted for the purpose of making a diagnosis. Then, if the diagnosis is grave, more aggressive treatment may be chosen.

An example might be a large mass on an extremity. If the pathologist returns a non-cancerous verdict, the mass might be handled conservatively, such as debulking. Debulking is a procedure in which a large portion of a mass is removed even though the entire mass cannot be. On the other hand, if the verdict is that the growth is likely to spread and endanger the health of the entire patient, removal of the limb might be indicated.

So, your veterinarian has removed tissue from your pet. What happens to it next? When it arrives at the pathologist’s office, a technician will take the entire growth from its formaldehyde-filled container and place it in a histiotome, a device to slice thin portions of the growth. Those thin slices are then affixed to a microscope slide and subjected to specially-colored stains that bring out the characteristics of the tissue that help the pathologist make a diagnosis. Using a microscope that can achieve very, very high magnification, the pathology doctor will examine the tissue’s most detailed points to come to a conclusion about the nature of the growth.

Notice I said, “come to a conclusion.” Tissue samples don’t come with little signs that say, “I’m a malignant melanoma,” or, “my diagnosis is…” Pathology is a very advanced science in the practice of medicine, but, like so many other diseases, many cancers look alike, even in the fine details under a microscope. Sometimes a judgement call has to be made as to the type of cancer observed. Sometimes the pathologist will give us a list of possibilities, from most to least likely.


Recall that the definition of “biopsy” includes the removal and analysis of fluids from the body as well as tissue. Examples include diseases of the chest cavity in which there is pus, transudate, modified transudate, exudate, lymph or chyle. In the abdomen, fluid collection caused by heart disease is called ascites. A traumatic encounter with a car might call for analysis of abdominal fluid to determine whether the urinary bladder has ruptured.

Sometimes fluid from a mass can give clues as to a diagnosis of the rest of the mass, and what treatments might be appropriate for the mass.

The pathologist the veterinarian’s  friend. He is an invaluable member of your pet’s doctor’s health care team, and his renderings on cytologies, histopathologies and fluid analyses can help chart the course for your beloved pet’s successful treatment.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.