Cytology Protocol

Cytology is a simple and useful diagnostic tool which can help the clinician in determining whether a lesion is inflammatory, infectious, or neoplastic in nature. In some cases, specific neoplasms can be diagnosed on cytology (e.g., lymphoma, melanoma, histiocytic sarcoma, haemangiopericytoma etc.) and therefore ensuring that high quality samples are submitted can result in more accurate results. Cytology in zoological, exotic, and aquatic species is generally underused, however, if suitably applied, the technique can allow the clinician to perform diagnostics without the use of sedation and general anaesthesia, which carry greater risks of complications in such species.

Suitable selection of relevant lesions, reliable sampling technique, good quality sample handling, and provision of a complete clinical history including a detailed lesion description enhances the pathologist’s ability to provide a more accurate cytologic diagnosis.

In short, a good cytologic diagnosis is a team effort.

Here, we provide some guidelines to aid in increasing the quality and, therefore diagnostic accuracy, of submitted cytology samples:

• Please complete the submission form, including a full animal signalment, relevant clinical history, and your clinical impression/differential diagnoses. Such details support correct interpretation of the pathologist’s findings.
• Clinical description of the lesion should include the location, size, shape, colour, and consistency, plus whether the lesion is single or one of multiple similar lesions.
• All slides must be labelled with the animal’s name or PON/AHEF number, the species, and the site so that sample identification can be verified.

Equipment Required

• Hypodermic needles: 21G (green) or 23G (blue); ¾ to 3 inch (depending on depth of tissue to be sampled)
• Personal preference on needle size
• 5ml syringe
• Microscope slides (with frosted labelling surface facing upwards)
• Hairdryer or cigarette lighter

Technique – continuous suction method:

• Insert the needle into the lesion with a 5ml syringe attached.
• With the needle in the lesion, apply 2-3ml suction pressure.
• Maintain suction and move the needle to and fro, redirecting the needle several times within the lesion.
• Disconnect the syringe from the needle base BEFORE removing the needle from the mass. You do this by holding the plastic base of the needle and twisting the syringe off the base. This releases the suction pressure and retains your sample within the needle.
        If you release suction before exiting the mass, you lose your sample…do not follow other guidelines on this point.
• Reconnect an air-filled syringe to the needle.
• Expel the contents of the needle containing the sample on to multiple microscope slides.
• Place a second new spreader slide horizontally and at right angles to spread the sample
• Use the frosted sides of both slides (i.e., 1st slide frosted-on-2nd slide frosted) – this makes the spreader into another useable slide for cytologic examination.
• Do not exert downward pressure that could rupture the cells.
• Using only the surface tension between the two slides, draw the spreader slide quickly and smoothly across the bottom slide (this is your sample).
• Dry these slides IMMEDIATELY using a hairdryer (applying heat at a distance so that your hand holding the slide is comfortable) or a cigarette lighter (at a distance, under the slide).
• This reduces drying artefact.
• If the heat applied is too hot – this can denature your cells, so keep heat source at a comfortable distance.
• Waiving the sample can lose cell yield if excessive fluid is present.
• Place slides into a slide box and send SEPARATELY from any histology samples to avoid formalin artefact.