Lumps and bumps that are cutaneous or subcutaneous often lend themselves very well to cytologic evaluation. They are easy
to get to and most animals don't require sedation or anesthesia for you to obtain these samples. Although a definitively diagnostic
sample isn't always obtained, the investment of time and equipment is minimal, and may give you the answer quickly and inexpensively.
Obtaining the sample
Proper sample collection and handling are key to getting a diagnostic sample.
What do you need?
- 21-25 gauge needles
- 3-20 ml syringes
- Microscope slides
- Stain – can be Wrights stain, Wrights-Giemsa, Diff-Quick, etc.
- A good microscope with an oil-immersion objective, immersion oil, and lens cleaner to clean it all off with!
- A good cytology book for reference
The skin is prepped as for a venipuncture. With a needle connected to a syringe (often 22 g needle with a 3-6 ml syringe),
immobilize the lesion and insert the needle, apply suction, release suction, and withdraw the needle. Depending on the mass,
the needle may be redirected within the lesion (without pulling back out through the skin. Don't expect to see material in
the barrel of the syringe-it's collecting in the needle.
After removing the needle, disconnect it from the syringe, fill the syringe with air, reconnect the needle and shoot out (gently!)
the contents of the needle onto the middle of a glass slide.
An alternative method involves "tattooing" a needle into the mass (making many quick jabs). A syringe filled with air is
then attached to the needle and the sample within the needle is expelled. This technique may lead to less blood contamination
and cell rupture in the sample.
After expelling the sample on a slide, smears are made by placing a clean glass slide on the surface of the sample, either
end to end or at right angles to each other, and gently pulling the slides apart, allowing the material to spread from the
weight of the slide. NOTE-you're not trying to squish the cells (they are fragile-treat them nicely), just spread them out
into a layer that is one cell thick so they stain evenly and you can evaluate individual cells. Make several slides if possible.
All slides should be allowed to air-dry before staining. No other fixation is needed and may actually damage the sample if
used. Don't heat fix cytology slides (that's for gram-staining only!) If you're submitting samples to an outside laboratory,
it is best to send unstained, air-dried smears (as well as any stained samples) separately from any formalin-fixed samples
you may also be submitting as the formalin fumes can destroy cytologic detail. If you're staining them to review in-house,
remember that you can use the same quick stains used for blood smears, but if the material is thick, you may need to both
fix and stain for longer.