What Is Cytology And When You Might Need One For Your Dog?

Written and reviewed by John A. Bukowski, DVM, MPH, Ph.D.
and Susan E. Aiello, DVM, ELS

Cytology is the examination of the cells under a microscope.  

This diagnostic technique can be used to characterize lumps and masses on the skin and in other organs of your dog.  It can also be used to evaluate cells from body fluids (eg, urine, joint fluid, fluid in the chest or abdomen) and body surfaces (such as the ear, skin, eye, mouth, vagina, etc).

Cytology often provides diagnostic information about your dog that can be useful in deciding on a treatment plan.  

For example, if cells from a mass appear malignant on cytology, your veterinarian will likely recommend that the mass is removed with appropriate follow-up treatment.

Mast cell tumor cytology. Image Joel Mills
Conversely, if cells from a mass appear benign, the mass can often be left and simply watched for any changes.

Cytology from a swab of an infected ear or from a skin scraping can reveal the presence of mites, bacteria, or yeast infections, and treatment planned accordingly.

Adult mite from skin scraping. Image: DermVet

Vaginal cytology can be used to characterize the estrous stage, or “heat cycle,” of a female dog, which can be used to determine the best time for breeding.

In a urinalysis, examination of the urinary sediment can reveal red and white blood cells, bacteria, or crystals that can indicate a urinary tract infection or other condition.

Cells are collected from a mass or lump by fine needle aspiration.  

In this procedure, a sterile needle is inserted into the mass and used to directly withdraw cells from the solid tissue.  This procedure can also be used to collect a sample of fluid from an organ or body cavity.

Ears are often swabbed with a Q-tip, and skin cells can be collected by scraping the skin with a small, sharp blade.  

In some cases, a microscope slide can be pressed directly on a lump or body part to create a smear for examination.

Fine needle aspiration, swabs, and skin scrapings are generally quick, relatively painless, and noninvasive procedures.  

In many cases, cytology can provide a great deal of clinical information and can sometimes yield a definitive diagnosis.  In other cases, cytology can indicate the need for additional, more aggressive testing (eg, taking a tissue sample for biopsy).