Using Cytology for Diagnosis

Cytology is the examination of blood or tissue under a microscope - and its advantage is that its quick and inexpensive. Heres how it can be helpful.


Discovering a lump or sore on your cat certainly does raise concern for the average cat owner. For one thing, nobody wants to worry for days to find out if it signifies a serious health problem. Cytology is a painless procedure that can provide a quick, inexpensive answer.

Cytology is the examination of cells under a microscope. This non-invasive, pain-free method screens for many health conditions, including inflammation, infection, fungi, parasites, bacteria and cancer. Cytology often can determine within minutes if your cat’s bump or that fluid in the abdomen should be cause for concern.

“A trained pathologist can look at cells and tell what kind of cells they are,” explains John Berg, DVM, a surgical specialist at Cummings School of Veterinary Medicine at Tufts University, and editor-in-chief of Catnip. “The veterinarian can make informed decisions about best treatment options once cells are identified.”

Fine needle aspirate used

Cytology is most commonly used to diagnosing a lump or bump. Cells are collected in a technique called a fine needle aspirate. This procedure uses a syringe identical to the one used by veterinarians to administer vaccinations. “We pass the needle into the mass and pull on the plunger of the syringe to draw material from the mass into the needle,” explains Dr. Berg.

A fine needle aspirate can be used to collect cells from masses on the skin surface, from deeper in the tissue, or even from a mass or fluid inside the chest or abdomen. For targets deep within a cat’s body, a longer needle may be required, as well as sedation to keep the cat from wiggling and an ultrasound probe to ensure that the needle doesn’t hit the wrong target.

“Cells that are collected aren’t very visible until they’re stained,” Dr. Berg says. “The cells are placed onto a slide to be examined under the microscope and then passed through a series of jars containing various stains, leaving the cells purple.”

Pathologists are specialists able to diagnose conditions by examining the cells under a microscope. Often they can distinguish benign from malignant processes by how the cells look, and sometimes can even identify the type of cancer.

Works best on certain tumors

But some tumors are more easily diagnosed with cytology than others, says Dr. Berg. That depends on how readily the tumor exfoliates (sheds cells). Some tumors don’t exfoliate very well and very few cells are collected during the fine needle aspirate.

Round cell tumors such as lymphomas exfoliate best and are very easy to diagnose with cytology. Carcinomas — basal cell and squamous cell carcinomas are two examples — arise from epithelial tissue such as the skin or the lining of the mouth or intestinal tract, and can also be readily diagnosed with cytology.

Tumors that don’t exfoliate well or are difficult to sample with a needle may not be candidates for cytology. For instance, sarcomas — tumors of connective tissue such as muscle, ligament and tendon — are often the most difficult to diagnose using this procedure. A biopsy may be needed in conjunction with a fine needle aspirate to get a definitive diagnosis of a cat’s fibrosarcoma, for example.

Dr. Berg says that biopsy is the gold standard for making a diagnosis because it preserves the tissue architecture. While cytology examines only a few individual cells, biopsy looks at a slice of tissue. The veterinarian collects a sample with a larger bore needle or makes an incision and removes a piece of tissue with a blade. After preserving the sample in formalin, it is embedded in paraffin wax, stained, and then fine slices are made. “The cells look the same under the microscope as with cytology, but biopsy preserves the relationship of cells to each other,” says Dr. Berg.

A pathologist can “grade” the seriousness of a cancer by evaluating the biopsy, an assessment of how bad this disease is likely to behave. “Grading can be done with biopsy but not with an aspirate,” Dr. Berg says.

A biopsy typically costs two or three times more than cytology because it requires general anesthesia, a pathologist’s report and a hospital stay. On average, it takes two or three days to get the results. But it offers a more complete and accurate diagnosis than cytology.

However, cytology almost always is your cat’s first step to getting a diagnosis. It doesn’t require a specialist or sedation, so the cost stays low. Dr. Berg estimates cytology costs average $25 to $50 to collect the sample, and that an outside pathologist’s report might cost between $100 and $150. These costs vary based on the region of the country and the veterinary clinic’s fees.

The sooner you have answers, the more quickly your cat can receive the proper treatment. Cytology is a fast, economical way for your veterinarian to diagnose many feline conditions. — Catnip staff


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