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.

Punch Biopsy
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
necessary.

Incisional Biopsy
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
cells.

Excisional Biopsy
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).

Endoscopic Biopsy
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
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
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
analysis.

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
second opinion.

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A biopsy allows your veterinarian to determine the types of cells in a tissue sample.

Biopsies are commonly used to determine if growths are cancerous but can also help determine the severity of a disease.

The tissue removed during a biopsy is examined under a microscope by a veterinary pathologist, a specialist in examining cells and tissue samples.

Some form of anesthesia is generally required to perform a biopsy.

What Is a Biopsy?

A biopsy is a surgical procedure in which a tissue sample is removed from the body and examined under a microscope. In some cases, only a small sample is removed for analysis. In other cases, several samples may be removed, or an entire growth may be removed and examined.

What Is a Biopsy Used For?

Dogs and cats commonly develop lumps and growths on their skin. Sometimes these lumps are cancerous, but in other cases, they are simply warts or other noncancerous (benign) growths. Examining a lump does not always give your veterinarian enough information to tell whether it is cancerous or not. A biopsy may be recommended to obtain more information about a suspicious lump.

A biopsy can also be used to diagnose a condition or determine the severity of a disease. For example, if an animal has liver disease, a sample of the liver can be removed (during a biopsy) and examined under a microscope to help determine the cause and extent of the liver damage.

How Is a Biopsy Performed?

Some form of anesthesia is generally required to perform a biopsy. Depending on several factors, including where the tissue sample(s) is/are located and how many areas need to be sampled, your veterinarian will decide whether to use local anesthesia, sedation, or general anesthesia. Local anesthesia usually involves injecting a medication in and around an area of the body to make it numb. If local anesthesia is used, your pet will likely be awake during the biopsy. In contrast, if sedation or general anesthesia is used, the patient is heavily sedated or completely asleep during the procedure. Sometimes, if a growth is on the surface of the skin and is very small, your veterinarian may be able to perform a biopsy using local anesthesia. However, if the area to be biopsied is within the abdomen, for example, or if multiple areas will be biopsied, general anesthesia is usually recommended.

Your veterinarian has a few options when deciding how to perform a biopsy and how much tissue to remove. In an incisional biopsy, a small sample of tissue is removed from a larger mass. In an excisional biopsy, the entire growth is removed and submitted for biopsy. Once the tissue is removed, your veterinarian will submit it to a diagnostic laboratory. There, a veterinary pathologist (a specialist at examining cells and tissue samples) will examine the tissue under a microscope to make a diagnosis. Results are generally available within several days.

What Are the Benefits and Risks of a Biopsy

Biopsies are very important for helping to confirm a diagnosis. With many types of cancers, early diagnosis is helpful for determining the course of treatment and can help increase the chance of survival. Biopsies can also help to confirm causes of other conditions, including skin lesions as well as diseases of the kidneys, liver, or bone marrow.

Your veterinarian will take many precautions to help ensure that your pet is safe during the biopsy and fully recovers afterward. To help reduce the risk of complications associated with surgery or anesthesia, your veterinarian may give your pet a full physical examination and check your pet’s blood work before the biopsy. Biopsies are very safe, routine procedures. The risks associated with a biopsy depend on several factors, including the overall health of the patient, the location of the area to be biopsied, and how many samples are taken. Be sure to discuss any questions or concerns with your veterinarian.

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Etiology and Pathogenesis

Anal sacs may become impacted, infected, abscessed, or neoplastic. Failure of the sacs to express during defecation, poor muscle tone in obese dogs, and generalized seborrhea (which produces glandular hypersecretion) lead to retention of sac contents. Such retention may predispose to bacterial overgrowth, infection, and inflammation.

Clinical Findings and Lesions

Signs are related to pain and discomfort associated with sitting. Scooting, licking, biting at the anal area, and painful defecation with tenesmus may be noted. Induration, abscesses, and fistulous tracts are common. In impaction, hard masses are palpable in the area of the sacs; the sacs are packed with a thick, pasty, brown secretion, which can be expressed as a thin ribbon only with a large amount of pressure. When the sacs are infected or abscessed, severe pain and often discoloration of the area are present. Fistulous tracts lead from abscessed sacs and rupture through the skin; these must be differentiated from perianal fistulas. Anal sac neoplasms are usually nonpainful and are associated with perineal edema, erythema, induration, or fistula formation. Apocrine gland adenocarcinomas of the anal sac are typically seen in older female dogs. These dogs may be presented for signs secondary to hypercalcemia, such as polyuria and polydipsia, or for problems related to the perineal mass.

Diagnosis of impaction, infection, or abscessation is confirmed by digital rectal examination, at which time the sacs can be expressed. Microscopic examination of the contents from infected sacs reveals large numbers of polymorphonuclear leukocytes and bacteria. A tumor should be suspected (anal sac apocrine adenocarcinoma) in anal sacs that are firm, enlarged, and nonexpressible even with irrigation. Ultrasonographic examination may be useful to determine whether a firm, nonexpressible anal sac is due to infection/abscessation or neoplastic disease. In the case of a suspected tumor, the diagnosis should be confirmed by biopsy. Regional and systemic metastasis should be evaluated, and serum calcium measured.

Treatment

Impacted anal sacs should be gently, manually expressed. A softening or ceruminolytic agent or saline can be infused into the sac if the contents are too dry to express effectively. Infected sacs should be cleaned with antiseptic, followed by local and systemic antibiotic therapy. Hot compresses, applied every 8–12 hr for 15–20 min each, are beneficial for abscesses. Repeated weekly flushings combined with infusion of a steroid-antibiotic ointment may be needed. Adding supplemental fiber to the diet may increase fecal bulk, facilitating anal sac compression and emptying. If medical treatment is ineffective, or if neoplasia is present, surgical excision of the sac is indicated. The closed technique for excision is preferred and has the lowest complication rate. However, fecal incontinence, a common complication of anal sac surgery, may result from damage to the caudal rectal branch of the pudendal nerve and may be complete if damage is bilateral. Chronic fistula formation may be seen when sac removal is incomplete or when the sac ruptures. Scar formation in the external anal sphincter may result from surgical trauma and result in tenesmus. (Also see Apocrine Gland Tumors of Anal Sac Origin.)

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Transmission or Cause: The cause of anal sac disease is unknown. Smaller dog breeds, such as Chihuahuas and poodles, are most often affected. Excessive anal gland production, soft feces or diarrhea, poor muscle tone, and obesity also contribute to higher risk of developing anal sac disease. Anal sac abscess tends to occur after an impacted anal gland has become so severely swollen and infected that the anal sac forms an abscess and ruptures.

Affected Animals: Although any dog can be affected, smaller breeds such as chihuahuas, dachshunds, and miniature or toy poodles are more commonly seen by veterinarians for anal gland problems. Cats suffer from the disease less commonly.

Overview: Anal sacs are the reservoirs for the secretions of anal glands which are located on either side of a dog’s anus, at approximately four and eight o’clock. These sacs contain liquid secretions from the anal gland, which, in healthy animals, are normally pale yellow-brown to grayish in color. The contents are usually emptied during normal bowel movements, or when a dog is nervous or scared. In most animals, these sacs empty easily. However, some dogs, especially small breed dogs, are not able to empty the sacs properly and become susceptible to anal sac disease.

A dog with anal sac disease may scoot across the ground in an attempt to relieve the sensation of pressure and irritation around its rectum. Dogs with this illness will also chase their tails and bite or lick their rear ends to alleviate the discomfort.

There are three progressive stages of anal sac disease. The three stages include anal sac impaction, anal sacculitis, and anal sac abscess. Anal sac impaction occurs when the liquid accumulates and thickens, causing the anal sacs to become distended and difficult to empty. A veterinarian can usually relieve the impaction by rectally squeezing the grape-like sacs individually until the thickened substance is expressed.

The second stage of the disease is known as anal sacculitis, or inflammation of the anal sac. In this stage, the anal sac material continues to accumulate and may become infected by bacteria. The third, and final, stage is abscess formation. This stage is the most severe and the most painful of the anal sac diseases. It may require surgical treatment. Sometimes the abscess can rupture through the skin, leaving an oozing red hole that is visible next to the anus. All stages of anal sac disease are treatable by a veterinarian.

Clinical Signs: Signs of anal sac disease include scooting across the floor; licking the area around the anus; tenesmus, or straining to defecate; biting or chasing the tail; discharge, swelling, or pain around the anal area; and behavioral change. When an abscess ruptures, a purulent discharge may be seen draining from the lesion. The area surrounding the abscess may appear red, swollen, and painful.

Symptoms: See Clinical Signs.

Description: Anal sac disease occurs in progressive stages: impaction, inflammation, and abscess formation. Impaction of the anal sacs occurs when the anal gland secretions contained in the anal sac thicken so that the sac is unable to empty during a bowel movement. Inflammation of the anal sac, or anal sacculitis, is an infection usually resulting from impaction; it may also be caused by bacterial growth within the anal sac.

During the sacculitis stage, the impacted fluid may become thinner and fill with pus. Abscess occurs when the inflammation of the anal sac has reached an extreme stage; at this point, a red-brown substance will be seen coming from the sac, which will be enlarged, hot, red, and very painful. Usually, the abscessed sac will rupture, leaving a hole near the side of the rectum that oozes a foul-smelling liquid. The tissues surrounding the abscess will swell up, and this will worsen the dog’s inflammation and pain.

Diagnosis: Diagnosis and staging of anal sac disease is made clinically with a rectal examination. Impacted or swollen anal sacs are often quite painful and some dogs may need sedation before a thorough examination can be done. Normal anal sac fluid is clear or pale yellow-brown; thick, brown or yellowish-green secretions are typical of animals with anal sac disease.

If the inflammation of the anal sacs has led to an abscess, a large, red, and swollen area may be visible on the side of the anus. A rupture of the abscessed sac can result in the oozing of a foul-smelling liquid material.

Prognosis: Expression, or applying pressure to the anal sac, is a successful method for removing impacted secretions from the anal glands, but in many cases, this procedure must be performed on a regular basis to prevent recurrence. Antibiotics most often eliminate the infection. If abscess has occurred, the abscessed anal sacs usually heal. However, all animals with anal sac disease usually have to have their anal sacs expressed on a regular basis to prevent further problems.

Treatment: When the anal sac disease is at the impaction stage, the most common treatment is an outpatient procedure called expression in which the veterinarian applies pressure to the anal glands until the thickened secretions are expelled from the sacs. Sedation may be needed if the dog is nervous or is in great pain.

For the anal sacculitis stage of the disease, the same expression procedure is performed; afterwards, an antibiotic-steroid combination ointment is applied directly to the anal sac. In addition, the examining veterinarian may prescribe oral antibiotics to help fight infection. To help determine the appropriate antibiotic, the veterinarian may also need to take cultures to identify what type of bacteria caused the sacculitis.

When anal sac disease is at the abscess stage, a surgical procedure is required if the abscess has not already ruptured. The veterinarian, after sedating the dog or placing it under general anesthesia, will surgically open the infected anal sac to clean out the infected material and drain the remaining liquid.

Following surgery for ruptured abscesses, an antibiotic-steroid combination ointment will be applied directly to the anal sac to fight infection and inflammation. An oral antibiotic probably will be prescribed as well. As in the treatment of sacculitis, culture of the abscess may be necessary to help determine the best antibiotic medication. If infection continues after the surgery, surgical removal of the anal sac may be required.

Prevention: Expression of the anal sacs every few weeks or months often will help prevent anal gland fluid from accumulating and becoming thickened again. High fiber diets have been shown to help prevent anal sac disease in at-risk dogs, especially those that are obese.

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