Veterinary cytology provides a quick, inexpensive and relatively non-evasive way to evaluate the cells in body fluids, skin masses and
increasingly (in conjunction with ultrasonography) internal organs. Inflammation, infection and neoplasia can often all be identified without the need for biopsy and anaesthesia. In our experience we find that often cytology is a much underutilised diagnostic tool and as one leading American oncologist said recently "Aspirate first, ask questions later".

All CTDS cytology submissions are analysed on site and we provide same day reporting on all fine needle aspirate and fluid submissions. Since it is crucial to correctly categorise body fluid submissions to confirm fluid origins, as well as a cytological report, we routinely include an absolute red and nucleated cell count, a quantitative protein, albumin & globulin measurements to assist in determining the origin of the fluid. Additionally for CSF (Cerebrospinal Fluid) submissions a Creatine Kinase (CK) and micro protein measurement is also included.

Cytology can reliably replace the need for surgical biopsy in a number of common diseases involving the skin and subcutaneous tissues.
A number of benign and malignant tumours such as histiocytoma, mast cell tumour, lipoma and anal adenoma have characteristic cytological features and can usually be definitively identified without the need for biopsy. Other tumours may be identified cytologically but their extent and nature (for example grade of a mast cell tumour or extent of infiltration) may not be characterised without histology. Even in this situation however cytology can often provide enough information to formulate a good diagnostic and therapeutic plan, and allow an owner to make more informed choices. Cytology tends to be of greatest value where lesions are discrete, free from ulceration and infection and involve epithelial cells or round cells predominantly. In contrast, diffuse poorly defined skin lesions and many deeper connective tissue lesions tend to yield less specific results and these often require histopathological evaluation to examine the architecture of the tissue as well as the individual cells.

Tips for fine needle aspirates from skin masses

• Use fine needles (23G), to collect the cells. Larger needles tend to cause more bleeding and may not increase cell yield.
• Make squash preparations of the aspirated material. This helps to spread cells into a thin layer and reduce artefacts associated
  with slow drying of the slides. Ring the lab if you want advice on making these or any aspect of sample collection and handling.
• Make 4-5 slides with some material from different areas of the lesion ( periphery, centre, deep border) to help ensure the slides are representative. The costs do not change between 1-5 slides at CTDS.
• Be selective about the lesions you aspirate initially to improve your chances of a diagnostic result. It may be worth trying aspirate cytology even on seemingly unpromising lesions however if the patient is not a candidate for sedation or anaesthesia and biopsy.
• For suspected tumours where the drainage lymph node is enlarged take node aspirates to check for metastasis.

Examination of pleural, peritoneal and pericardial fluids can help to define the nature of the disease process causing the effusion (true transudate, modified transudate, exudate) and in some cases can allow a specific diagnosis to be made (pyothorax, malignant neoplasia, bile duct rupture etc). The type of fluid identified is given in the "Cytological Interpretation" section of the report and is based on evaluation of the cell counts, protein content and cytological findings. A list of differential diagnoses for the type of effusion is incorporated in the "Comment" section of the report.

Tips for body cavity fluid samples

• Minimise blood contamination of the sample and trauma by using fine gauge needles or wing vein catheters to collect samples.
• For pleural fluid collection enter the rib space just in front of the rib to avoid laceration of the vessels running down its caudal aspect.
• Collect and submit the sample in EDTA blood tubes. EDTA helps to prevent clotting and assists cell preservation.
• Fix part of the sample with 10% neutral buffered formal saline. Add 2 drops per ml of fluid. Buffered formalin is provided in our histopathology pots. Label the fixed sample, with an "F" or similar, as a separate staining system is used for this. Always submit a plain sample and it is helpful to make a couple of smears of the fluid whilst it is still fresh. These do not need to be stained but must be kept away from any formalin fumes.

Mesothelial cells line body cavities.
When these become reactive, which commonly occurs where there has been an effusion present for some time, their appearance can mimic malignant epithelial cells. Where cytology suggests an epithelial malignancy is likely it is always advisable to confirm this by checking for the presence of a mass by means of ultrasound or post drainage radiography. Pericardial effusions present particular problems in this regard and cytology cannot reliably differentiate between neoplastic and non-neoplastic effusions from this site. Ultrasound, measurement of fluid pH at the time of collection and cytology together are required.

Examination of synovial fluid can help differentiate degenerative and inflammatory joint diseases and can be particularly helpful in animals with multiple joint problems, refractory lameness and as part of the work up of pyrexia of unknown origin. As the cytological changes in degenerative joint disease (DJD) are often mild and relatively non specific the diagnosis requires the combination of the history, physical examination and good quality radiographs. Please include the latter information on the submission form wherever possible.

What you need to send: Air dried smears, sample in EDTA, (Swab in transport medium if possibly septic)

Tips for Synovial fluid samples

• Degenerative changes in synovial cells form an important of the cytological diagnosis of DJD. These changes can be mimicked however by in-vitro changes in cells during transit to the lab. For this reason it is very important to submit air dried smears as well as a sample in EDTA.
• Small, uncontaminated samples are better than larger samples containing lots of aspirated blood. Stop aspirating if blood suddenly starts to appear in the sample at collection, even if the sample is very small. Often a diagnosis can be made from a single drop of fluid smeared on a slide. Conversely, heavily bloodstained samples are often of little use and have to be repeated. If you see blood contamination occurring at sampling , state this on the request form.
• EDTA samples are preferable to plain samples for synovial fluid and are suitable for cell counts, viscosity determination, mucin clot test and cytology.
• Where septic arthritis is differential, place a small amount of fresh synovial fluid on a swab in charcoal transport medium and submit this together with the smears and EDTA sample. Only around 50% of septic joints have a positive culture so a negative culture result does not exclude this possibility.
• When examining patients with multiple joint swellings:
  • Collect fluid and smears from the larger joints (stifles, shoulders, elbows)
  • Collect smears only from the small joints (carpi, tarsi, metacarpophalangeal joints)
  • Take serum for appropriate serology, dependant upon the signs , history and X-ray findings – contact the lab if you want advice on test selection for these.
• If the radiographic findings are equivocal, submit the X-rays with the synovial fluid for interpretation by a Diplomate Radiologist ( see telemedicine). The differentiation of erosive and non erosive polyathropathies from the radiographs can significantly alter the differential diagnostic list and the prognosis in some cases.

CSF examination can be useful in the diagnosis of inflammatory CNS disease in particular which is often associated with multifocal neurological signs and pyrexia. Routine CSF examination is advisable in animals having myelography and can be part of the investigation of pyrexia of unknown origin. The major challenge in CSF examination is the very low cellularity and rapid lysis of cells in such a low protein environment. Both of these problems can be overcome by fixing part of the sample immediately after sampling.

Tips for CSF samples

• Discard the first few drops of collected CSF as this is likely to have some degree of haemic contamination.
• Collect two samples into EDTA tubes. Submit one for protein and CK assay and cell counts.
• To the second EDTA sample add 1-2 drops of 10% neutral buffered formal saline. Buffered formalin is provided in our histopathology pots. Label the fixed sample with an "F" or similar, since a separate stain is used for the cytological examination of fixed samples and to verify the cell counts.
• Where there is focal spinal cord disease, obtaining the sample from a site caudal to the lesion ( usually the lumbar cistern) is likely to increase the diagnostic yield.
• Where sample volume is very limited (less than 0.5ml) submit an unfixed EDTA sample only and prioritise the tests you need on the sample.

Techniques for nasal, tracheal, broncho-alveolar, prostatic and (in birds) crop washings are well described and widely available but if you require assistance please contact the lab. Simple steps in sample handling however can significantly increase the diagnostic yield from these procedures.

Tips for Washings

• Submit the fluid samples in EDTA, one fixed one unfixed (see body cavity fluids). Fixation is essential for washings to stop the rapid lysis of collected cells during transit.
• Make smears from the catheter tips after washing and submit these. Often the smears from the material adherent to the catheter is of greater diagnostic value than the fluid itself.
• If the washing fluid contains flocculent material, pick some of this out with a sterile hypodermic needle and make smears from it for submission.
• For nasal flushes, fenestrate the catheter by making holes in it with a hypodermic needle and scrape it vigorously against the mucosa to increase the cellular yield. Ideally couple this with rhinoscopy and nasal radiography using intra-oral film.
• Where bacterial infection is suspected submit charcoal swabs of the fluid or cellular material along with the fluid. Avoid contamination from external surfaces such as the oropharynx , nares or skin where the presence of large numbers of normal commensal organisms may overgrow or suppress significant isolates.