Few things seem to strike more fear into the hearts of pet parents than hearing these words from your veterinarian: “I’m recommending a biopsy.” The fact is, many pets at some point in their lives will undergo a biopsy procedure.
As pets get older, their chances of developing abnormal growths and/or cancer increases. A biopsy is used to determine what abnormalities may be cancerous and which are benign (non-cancerous).
What is a Biopsy?
The term “biopsy” refers to the removal of a sample of tissue directly from a specific part of the body – usually from a tumor, the skin, or an organ – and examining the cells that make up that tissue under the microscope. Your veterinarian may recommend a biopsy for anything that looks suspicious: a lump under the skin, a scaly or pigmented area of the skin itself, or a bone or organ that appears abnormal on an x-ray or ultrasound.
Many tissues and organs can be biopsied, including the skin, lymph nodes, liver, kidneys, lungs, spleen, glands (such as the prostate and thyroid), and bone.
How Tissue is Collected and Examined
There are several different biopsy techniques used for collecting tissue and cells. The most common are the punch biopsy, needle core biopsy, wedge biopsy, and excisional (also called “surgical”) biopsy.
Which technique is used is ultimately determined by the specific properties of the area to be biopsied – including location, how easy it is to get to, and the type of tissue being sampled. The condition of the individual pet is also taken into consideration, since some biopsies require general anesthesia.
During this procedure, a tool called a biopsy punch is used to remove a small, deep circle of tissue from either the skin or a growth (also referred to as a “mass”). The skin is then closed with just one suture. This technique is especially good for use on scaly lesions on the surface of the skin, and it’s minimally invasive, requiring only local anesthetic.
Needle Core Biopsy
A needle core biopsy uses a specialized hollow needle instrument to take a long, thin piece of tissue from the center of the mass. It can be used for growths located both on the outside and inside of the body (using imaging technology such as ultrasound to help locate the area to be tested).
The needle core biopsy is often used on pets with skin masses. It is minimally invasive (often done with local anesthesia and/or sedation), and relatively inexpensive. No sutures are required.
The wedge biopsy (sometimes called an “incisional biopsy”) is more invasive than a punch or core biopsy. It’s used in cases where punch or needle biopsies can’t provide adequate tissue to make a diagnosis.
Wedge biopsies involve the surgical removal of a wedge-shaped piece of tissue from the suspected mass for examination. This type of biopsy is usually recommended for abnormalities in internal organs, and requires general anesthesia. Because this procedure is more involved, some veterinarians may elect to have a wedge biopsy done by a veterinary surgery specialist.
In an excisional (or surgical) biopsy, the entire mass (rather than just a piece of it) is removed, along with the surrounding tissue. This is done to make sure that all margins of the mass are collected.
Excisional biopsies are used not only to distinguish between cancerous and benign tumors, but they can also differentiate between certain types of cancers. They may also be used to help diagnose a disease (such as liver disease), and to determine that disease’s severity.
Excisional biopsies tend to be the most accurate and informative, but they are also the most invasive. General anesthesia is required for a true mass removal.
What Happens After the Biopsy Procedure?
Once a tissue sample has been collected, it’s placed in a small plastic jar containing formalin, a toxic (and very pungent-smelling) solution derived from formaldehyde. This preserves the individual cells making up the tissue, which essentially provides a “snapshot in time” of the sample for the veterinary pathologist who will be examining it.
The jar is then sent to a lab. There, the tissue is removed from the formalin, covered in wax, and sliced into extremely thin sections. These almost transparent sections are placed onto glass slides and stained with a specialized solution, which helps the pathologist better identify the morphology (specific shape, size, and structure) of the cells within the tissue.
Cell morphology indicates whether the sampled cells are cancerous, and if so, what type of cancer is present. If the cells are not cancerous, and they were taken from an organ such as the liver or kidney, the appearance of these cells can still indicate if disease is present, and if so, how advanced it is.
Once the pathologist has prepared a formal report, the report is sent immediately to the veterinarian who requested the biopsy. The veterinarian may then consult with the pathologist to interpret the results, and in some cases, obtain additional insight to assist with formulating a treatment plan for the pet.
Cytology vs. Biopsy
Sometimes your vet may elect to do a procedure called a fine needle aspirate (or FNA) first, rather than proceed straight to a biopsy. The difference between these two procedures can be somewhat confusing. The FNA is considered to be “aspiration cytology”, which is a much simpler procedure than a biopsy.
With aspiration cytology, the veterinarian inserts a long, thin needle through the pet’s skin directly into the tissue being sampled (usually a skin mass or enlarged lymph node). He or she then repeatedly pumps the plunger in the syringe to suck up as many cells as possible for sampling. These cells are squirted onto a glass microscope slide, then sent to the lab for staining and evaluation by a pathologist. Sedation or anesthesia is usually not required for an FNA.
Cytology is often used to gather preliminary information first. It doesn’t provide as much information as a biopsy, but the results can help your vet determine in which direction to proceed. It can tell the vet if a growth is indeed a tumor, and if so, what family of tumors it might belong to (which will determine what treatment is needed).
With FNA, results are usually available more quickly than with a biopsy. If more specific information is needed after an FNA, your vet may then recommend a biopsy.
Nothing to Fear
Biopsies are no different from any other procedure when it comes to risks vs. benefits. Some pets are not good candidates for biopsy procedures. If a veterinarian suspects a tumor in a place that is not accessible for a biopsy (such as a brain tumor), or if the pet has a bleeding disorder that could result in excessive bleeding during the procedure, the vet may elect to use his or her best guess as to what is causing the problem and treat it accordingly. Fortunately, these cases are rare, and most pets do quite well during biopsy procedures.
It’s also important to note that there are several options available when it comes to managing discomfort during biopsies. In some cases where a pet is not a good candidate for general anesthesia, a combination of a sedative and a local anesthetic may be a better alternative.
One word of advice: when it comes to lumps and bumps, beware the “just watch it” approach. Many types of cancer can be caught in the early stages, and it’s relatively easy to perform a simple biopsy to obtain an accurate diagnosis to determine what treatment, if any, is needed.
Fearing a biopsy for your pet could result in delayed treatment, which can greatly impact his health. It’s always better to know what’s happening and address it head-on than not to know! If your pet ever needs a biopsy, rest assured that your vet will work with you to determine which technique is the safest and most effective for your pet.
Has your pet ever had a biopsy? Please share your story with us in the comments below!