When it comes to taking samples for skin cytology, there is no one technique that is best in every situation. Here are my favorite techniques, and when I find them most useful:
1. Cellophane tape stripping is the technique that I now use most often. It is great for relatively dry, scaly, seborrheic skin and for getting into tight corners, like the interdigital spaces. Inexpensive clear cellophane tape, a glass slide, a modified Wright’s stain kit, and a good microscope are all that you need. Most veterinarians have the first three; if you don’t have a good microscope that allows you to see clearly with the oil immersion lens, invest in getting it cleaned up or replaced.
To make a sample, tear off a 2-inch piece of tape and press it against the affected area(s) several times. If the body regions are clinically distinct, make multiple samples. Place the tape loosely on the slide to transport it to your laboratory, peel of the tape and dip it directly into the dark blue stain for 5-10 seconds, then place it on the slide. Blot it with bibulous paper and you are ready to examine it in less than a minute.
2. Direct impression with a glass slide works great if you are interested in a greasy or moist area, which will transfer sufficient material to the slide. Again, press it 2-3 times in the affected area(s), let it air dry, then follow the staining technique above.
3. Cotton swabs are the least used technique, but may be helpful when you need to reach into the crevice of a Bulldog’s tail fold, or some similar situation. Roll out the swab as you would an ear swab, then stain it as above.
4. Pustule cytology samples are taken by pricking a pustule with a 25g needle and smearing the contents on a glass slide. These are best stained with the full complement of 3 stains in your modified Wright’s stain kit.
That’s it! Skin cytology is one of the most widely used and informative tests performed by veterinary dermatologists. Make it part of your diagnostic work up of skin cases too!