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What Is Cytology

Veterinary Cytology Offers Quick Diagnosis


When owners discover a lump or sore on their puppy, cytology can offer quick answers about how serious the problem might be. While pricy diagnostic tools like MRI or CT-scans of advanced vet care provide detailed information, one of the simplest tests offers quick, inexpensive answers.

“A trained pathologist can look at cells and tell what kind of cells they are,” says John Berg, DVM, a surgical specialist at Cummings School of Veterinary Medicine at Tufts University. Once cells are identified, the veterinarian can plan the most appropriate treatment.

Your veterinarian may use cytology to figure out the cause of that sunburn sore that won’t heal, or a lump that arises on your puppy’s body. Cytology can detect many health problems, including inflammation, infection, fungi such as ringworm, parasites, bacteria, and cancer.

What Is Cytology?

Cytology is a noninvasive, pain-free way to look at cells under a microscope. Cytology often can determine within minutes if the pup’s lump or bump is cause for concern.

Cells are collected by using a fine needle aspirate. The veterinarian uses a syringe similar to those used to give 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,” Dr. Berg. A fine needle aspirate can be used to collect cells from masses on the skin surface or from deeper in the tissue. For masses inside the chest or abdomen, a longer needle would be required, as well as sedation and an ultrasound probe to guide the needle to the right place.

“We squirt the cells onto a microscope slide, and they’re examined under the microscope,” says Dr. Berg. But first the slide is dunked into a series of jars of fluid that contain different stains, leaving the cells purple. “Cells aren’t very visible until they’re stained,” he says.

Pathologists look at the stained cells under a microscope. Often they can distinguish benign from malignant processes by how the cells look, and sometimes even identify the type of cancer. Some tumors are more easily diagnosed with cytology than others. That depends on how readily the tumor exfoliates—sheds cells. “Some tumors don’t exfoliate very well and we stick a needle in and we don’t get very much,” says Dr. Berg.

Types of Cells Cytology Can Diagnose

Round cell tumors such as mast cell tumors and lymphomas exfoliate best and are very easy to diagnose with cytology. Carcinomas that arise from epithelial tissue such as the lining of the mouth or intestinal tract also can be diagnosed with cytology. Benign fatty tumors (lipomas) occur under the skin and are very common in dogs and typically aren’t a serious problem. “They are very easy to diagnose by an aspirate,” says Dr. Berg, although not many cells are collected that way. “We just get this clear fatty-looking greasy material and we know it’s a lipoma. We don’t even try to stain those to look at under the microscope.”

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 cytologically. A biopsy may be needed in conjunction with a fine needle aspirate to get a definitive diagnosis.

What is A Biopsy?

Biopsy is the gold standard for making a diagnosis because it preserves the tissue architecture. Instead of a few individual cells, biopsy obtains a piece of tissue either with larger bore needle, or an incision that removes a piece of tissue with a blade. The sample is preserved in formalin, 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.

That’s important because biopsy samples allow the pathologist to “grade” the seriousness of a cancer—an assessment of how malignant and bad it’s 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 hospital stay. It also takes two or three days to get the results. But it offers a more complete and accurate diagnosis.

Veterinarians almost always perform cytology as the first step in diagnosis, though, because the procedure can be done in the exam room with no sedation. The cost might run $25-50 to collect the sample, and another $100-150 if sent out for the pathologist report. Cytology is a fast, economical way for your veterinarian to determine next steps for your puppy’s diagnosis and treatment—and in happy cases, quickly gives owners the good news that the lump is nothing to worry about.

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