Ensure you know the fundamentals
When a dog or cat presents with an intraoral or extraoral mass, the veterinarian has many options, including treating medically,
removing a small sample for histologic examination or performing a wide excision to effect a cure. Determining if the lesion
is secondary to inflammation or malignant neoplasia can be most helpful when choosing further diagnostic and treatment plans.
Becoming familiar with the fundamentals of oral cytology and using it in your dental practice can be invaluable.
Photo 1: A cotton swab used to obtain cellular sample from a mandibular swelling in a 5-month-old Labrador Retriever.
Obtaining a sample
Diagnostic cytology samples from the oral cavity can be collected using a swab, scrape, touch impression or fine needle. A
swab of the exfoliated cells from an oral lesion (Photo 1) can be rolled onto a clean slide for microscopic examination.
Unfortunately, not all masses exfoliate diagnostic samples. Rubbing a swab over an encapsulated mass usually will not yield
a diagnostic/cellular sample.
Impression smears of lesions can be frustrating to interpret, because they often reflect superficial infection and inflammation
but not the underlying cause of the mass. If in doubt, both impression smears and aspirates should be attempted, with careful
labeling of slides as to which represents what type of preparation.
For a fine-needle biopsy, two methods are commonly used to obtain diagnostic samples: non-aspiration and aspiration techniques.
With the non-aspiration variety, pull the plunger back several milliliters to allow air to enter the syringe. Then place a
20-ga needle multiple times into the tissue to harvest core samples. Push the sample out on a slide, and compress it for preparation.
For the aspiration method, insert a needle into the mass, and retract the syringe plunger to create negative pressure. Redirect
the needle after releasing pressure several times without exiting the mass. Remove the needle from the syringe, and then fill
it with air. Reattach the needle, and expel the sample from the needle onto a clean slide. Stain the slide with a modified
Wright's stain (Diff-Quik—Dade Behring) (Photos 2A-2D).
Photo 2A: A mature cat with a left facial enlargement.
Photo 2B: Fine-needle aspiration of the enlarged facial area.
Photo 2C: A mixed inflammatory cell population consisting mainly of neutrophils with two macrophages.
Photo 2D: Resolution of the facial enlargement after removal of multiple root fragments.