Also known as cytopathology, cytology is a cost-effective and common diagnostic procedure in which the veterinarian or a specialised laboratory examines the structure and function of cells under a microscope. Cells are the smallest living entity and are found in all living organisms. They are made up of the cell membrane, cytoplasm and the nucleus, which contains the DNA. Animals and plants are made up of trillions of different types of cells which have diverse tasks, bacteria, some fungi and protozoa are single-celled organisms.
Examples of cells in cats include:
- red blood cells
- white blood cells
- muscle cells
- brain cells
- nerve cells
- bone cells
- stem cells
- skin cells
- endothelial cells
- fat cells
- eggs and sperm
George Papanicolaou was a Greek physician who pioneered the use of cytology to evaluate the cells of the cervix in women, hence the name pap smear.
What does cytology reveal?
The word cytology comes is derived from the Greek word kytos, which means cell and logy which means study and can provide information on the following:
- Growths and masses (benign and cancerous cells, cysts and other abnormalities)
- Abnormalities with the internal organs
- Fluids (washes which include bronchoalveolar lavage ad transtracheal wash, urine, cerebrospinal fluid, joints, pericardial fluid, body cavity effusions, cysts, vaginal fluid, blood)
- Microbial infections (bacterial or fungal) from skin, ears or internal tissues
How is cytology performed?
Cytology is performed in several ways depending on the tissue sample required and location.
- Fine needle aspiration (FNA): This technique uses a fine-gauge needle which is inserted into the tissue and the plunger is pulled back to suction to remove tissue, cell or fluid samples.
- Skin scraping: A scalpel blade to gently scrape along the surface of the skin or a lesion and can be useful for the diagnosis of skin mites, fungal and bacterial infections and cancer.
- Swab: A q-tip (cotton bud) is used to collect discharge or skin cells from the skin, mouth, ears, nose and vagina.
- Imprints: A glass slide is pressed against and gently rolled against an ulcer or lesion to obtain the sample. Dry scabs and crusts are removed before the impression.
Samples from internal organs will require anesthesia and ultrasound to guide the veterinarian.
Once the sample is obtained, the veterinarian smears the sample onto several slides and allows the sample to dry, he or she then adds a biological stain which helps to identify the cells and nucleus. The sample is then evaluated by the veterinarian or sent to a veterinary pathologist for diagnosis.
Under the microscope
During an evaluation, the sample is smeared on a glass slide and stained, the pathologist looks at:
- type of cells
- size and shape of the cells (normal, abnormal, inflammatory, bacteria, fungus, yeast)
- size and shape of the cell’s nucleus
- arrangement of the cells
- type of cancer
- grading of the cancer
Is cytology painful?
Cytology is generally a painless procedure, although some cats may experience minor discomfort from the fine needle aspiration. Due to the small diameter of the needle used, this will be minimal. Anesthesia or sedation is unnecessary in most cases.
Frequently asked questions
What is the difference between cytology and histopathology?
Histopathology is an examination of whole tissues (for example a uterus, spleen, entire tumour) compared to cytology which is the study of cells.
Is cytology the same as biopsy?
No, cytology is the microscopic examination of cells and biopsy is the extraction of cells or tissues for examination. A biopsy is sometimes provided for cytological examination.
How long do cytology results take?
If the veterinarian is evaluating a cytology sample, the results will only take a few minutes. If the sample is sent away for evaluation, the results will take between 1 and 2 days. Most cytology samples evaluated in-house are for simple diagnostics such as an ear infection, skin mites or skin infection, whereas a suspected tumour will require a veterinary pathologist.
How much does cytology cost?
This depends on the sample and if it is evaluated in-house or sent to a veterinary pathology, and can cost anywhere from $80 to $200.
Feature image: Carcinoid tumour of the lung courtesy Ed Uthman, Flickr