What is biopsy?
A biopsy refers to a procedure that involves removal of cells or a piece of suspicious tissue for a detailed analysis by a
specialist called pathologist. It is the most common and most certain way to determine whether the suspected mass is
cancer or not. When only a sample of tissue is removed, the procedure is called an incisional biopsy or core biopsy. When
an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. When a sample of tissue or
fluid is removed with a needle, the procedure is called a needle aspiration biopsy.
What are the different biopsy methods?
Several different biopsy techniques are used to obtain samples of cells or tissues. A technique of choice will depend on the
location of the tumor, the suspected type of tumor, the analysis to be done, the pet’s condition and/or the veterinarian’s
preference. Sometimes, the location of the tumor will be inaccessible or would make the procedure too dangerous for the
pet. In such case, the veterinarian will have to rely on combination of other diagnostic tests. The more commonly used
techniques by veterinarians are needle core biopsy, punch biopsy, incisional biopsy, and excisional biopsy. Specialized
biopsy techniques include endoscopic biopsies, laparoscopy, thoracoscopy and image-guided biopsy.
Needle Core Biopsy
This type of biopsy uses several types of needle instruments to obtain the tissue sample. This method can be used for
masses located on the outside of the body as well as inside of the body with the help of imaging technologies. Most needle
core biopsies are done with local anesthesia or sedation without the need to hospitalize the pet and are fast, safe, easy,
generally accurate and relatively inexpensive.
During this procedure, a thin, hollow needle removes tiny tissue samples from the mass in question. The veterinarian will
remove several samples from the mass to get as many different cells as possible so that the pathologist can make an
accurate diagnosis. Not all needle core biopsies will result in obtaining diagnosis, and in some cases, subsequent incisional
or excisional biopsies may need to be performed.
This type of biopsy is used to obtain a shorter and wider sample from externally located masses such as on the skin, in the
mouth or around the anal opening. The veterinarian will use a punch biopsy tool to make a cut into the mass, the mass
sample will be lifted and the base of the sample will be cut from the base with scissors. One or two sutures may be
This type of biopsy is used in cases where punch or needle biopsies cannot provide adequate tissues or when no
successful diagnosis was obtained. It is generally recommended when the results of the biopsy will affect the treatment
decisions. It involves a surgical removal of a piece of tissue from the suspected mass for examination and must be
performed so that it does not compromise subsequent treatment or contaminate healthy tissues with the possible tumor
In this type of biopsy, the entire mass rather than a piece of the mass is removed for evaluation. This technique is feasible
if the mass is small, freely movable, and without adjacent tissue invasion (otherwise the tumor may be spread throughout
the biopsy site and may be more difficult to treat later).
Endoscopy is a diagnostic procedure in which a fiber-optic tube is inserted into a lumen or cavity of the body to visualize
any abnormalities and to take samples of tissue for analysis. This procedure is done using a thin, flexible lighted tube with
a viewing lens or a video camera. If a video camera is used, it is connected to a monitor that allows the veterinarian to
clearly see any masses in the area. These techniques allow to visualize and collect biopsies from tissues such as the
esophagus, stomach, lung, liver or other organs without the need for a large surgical incision. These methods are less
invasive than surgery and decrease the amount of pain, bleeding and recovery time.
Laparoscopy is similar to endoscopy but is used to examine the contents of the abdomen. The veterinarian inserts a
special fiber-optic tube called laparoscope through an incision in the abdomen to visualize internal organs such as the liver
or spleen and the laparoscope sends images to a monitor. The doctor uses the monitor to manipulate the instruments
attached to the tube to remove tissue samples for further examination.
Thoracoscopy is a diagnostic procedure in which a fiber-optic tube is inserted into the chest cavity to visualize organs such
as the lungs. As is the case with endoscopy and laparoscopy, the veterinarian will collect tissue samples for further
Interpretation of Results
The job of the pathologist is to determine if the tissue sample comes from a tumor, if it is benign or malignant, what type it
is and how advanced it is. The interpretation of results can be dependent on the quality and quantity of the sample
submitted to a pathologist for evaluation and not all pathologists will come to the same interpretation even if dealing with
the same sample. The veterinarian should interpret the results in the context of clinical symptoms of your pet and consult
with the pathologist if there is any doubt about the results. The owners should keep in mind that it does not hurt to have a