What Is A Biopsy? Images And Answers To Questions About Biopsies In Dogs And Cats

Health care questions and answers about puppies and dogs

What is a tissue biopsy?
Questions and answers about tissue biopsy
procedures in dogs and cats

A biopsy is a procedure whereby living tissue is removed from a patient. Biopsies are very useful in human and veterinary medicine to identify pathogenic organisms, classify cells as normal or abnormal, and for evaluating types and stages of cancerous tissue. The specimens are analyzed by a practitioner or in many cases sent to a pathology lab for examination by a specialist in human or veterinary pathology. Many cases require microscopic evaluation in order to establish a definitive diagnosis!

Health care questions and answers about cats and kittens

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Question:
    My veterinarian thinks my dog may have a kind of leukemia called malignant lymphoma because his (the dog's!) lymph nodes are all very swollen.
     My dog acts just fine but the doctor wanted to take a biopsy of one of the lymph nodes to find out what is causing them to swell so much. He stuck a needle into the lymph node behind his knee and is sending it in to a lab.
     Is this really a biopsy and what is it going to tell us?

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Answer:   biopsy... lymph node... what is
     Being able to actually look at cells under the microscope and see what kind they are, determine if they are normal or not, and classify them according to well established scientific standards is an amazing tool for human and veterinary medical doctors. The ability to use special stains to highlight certain cells that otherwise would be hidden from view is an important part of the cell identification process.
     The dark blue cells in the image on the right shows how a special stain makes the pathogenic (disease producing) yeast cells of Blastomycosis really stand out from the background of lymph node cells. This specimen was obtained by doing a FNA (fine needle aspirate) where a needle is inserted into the lymph node and tissue cells pulled into the needle.
     Even a few cells when placed on a slide and examined under the microscope could yield a positive diagnosis. And the sooner a positive diagnosis is made the sooner the patient can start on an appropriate therapeutic plan.

         Doctor's Notes
     Tissue specimens that aren't easily identified by visual inspection can be sent to a veterinary pathology laboratory. Your veterinarian will suggest sending off tissues for positive identification and classification.
      You can always decline the service, but knowledge acquired today may make life better tomorrow!

Needle biopsies...
     Needle biopsies seldom cause pain for the patient and can be a quick and efficient method of tissue analysis.

Learn about tumors...
What's the difference between a tumor, growth, cancer, lump, mass, etc. Go here.

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A 22 gauge needle is used to obtain cells from a swollen prescapular lymph node. This is called a Fine Needle Aspirate (FNA)	Cells and fluid are visible in the syringe. Often only a tiny amount of specimen is in the needle and is then placed on slides.	The aspirated sample is "squirted" onto glass slides, dried, stained and examined under the microscope.	Specimens are thoroughly evaluated either in the clinic or sent to a veterinary pathology lab for analysis.

This is a medium power microscopic view of abnormal lymphocytes from a swollen lymph node.	Surgical sections of tissue are placed in a preserving solution for transport to a veterinary pathology laboratory.	This tumor was first analyzed via FNA and found to be benign. A reasonably wide margin is left close to the growth.	To avoid leaving any tumor tissue, the incision is made about 1/2 inch away from the visible tumor mass.

This biopsy was done using a trephine to obtain a sample of bony tissue	You can see how the trephine plunger pushes the sample out for storage in preservative.	Impression smears of superficial tissue cells are obtained by pressing the glass slide onto the abnormal lesion	This invasive tumor might well be identified and classified using just an impression smear.

Question:
I'm wondering if I should let my vet do a biopsy of a small nodule on my dog's skin. Apparently it could be what my vet calls a mast cell tumor. How is a biopsy done and why shouldn't the doc just remove it and be done with it?


Impression smear is done	Excisional biopsy is done

View the website of the
American College of Veterinary Pathologists

Answer: biopsy... what kinds... why do
There are several methods for doing a biopsy...
EXCISIONAL... indicates the entire mass or growth is removed and analyzed.
INCISIONAL... means a small portion of the mass is excised with a scalpel.
PUNCH... is the use of a circular scalpel or trephine is pressed into the tissue mass and a small plug of tissue is obtained. See the images above showing a bone biopsy done with a trephine.
NEEDLE BIOPSY... is a fine needle aspirate (called a FNA) using a syringe and needle that "vacuums" into the needle a small amount of tissue.
CURETTE... means scraping or curettage of the affected tissue.
IMPRESSION SMEAR... is done with a glass slide pressed against gently cleaned abnormal tissue.

     In your case the doctor probably needed to know what kind of tissue is present so a proper plan of action can be done prior to removal. If the tissue is benign with little chance of spreading (metastasis) or of regrowth in the same area the surgical excision strategy will be quite different from the procedure needed to remove an invasive tumor such as a mast cell tumor.
     Mast cell cancer is common in dogs and there are stages an individual growth may have relating to "nastiness". Some are much more malignant than others but in most cases of mast cell tumor a wide and deep excision must be done. If a growth is benign, the surgeon can be less aggressive regarding removal of adjacent normal tissue.
     To summarize, your veterinarian wants to know what it is before surgery is done because "what it is" greatly influences "what to do".