Page 24 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

Collection, Preparation

VetBooks.ir 2 and Staining of Cytology

Specimens

2.1 Materials

• Needles (21–25G) and syringes (2–10 ml) for fine-needle sampling of cutaneous and
subcutaneous masses with/without aspiration.
• Cotton swabs, ideally dampened with saline, for swab sampling.
• Glass slides, possibly with frosted end for ease of labelling and identification.
• Plain and EDTA tubes for fluid specimens (e.g. cystic, fluid-filled lesions, abscesses, etc.) for
culture and cytology, respectively. The EDTA sample is not suitable for culture, due to its
bacteriostatic effect.
• Slide holders to protect smears from breakage when sent to an external laboratory for evaluation.

2.2 Sampling Techniques

Fine-needle sampling with aspiration
• Advantages
Suitable for sampling most skin lesions, especially those with poor tendency to exfoliate
(e.g. mesenchymal proliferations).
• Disadvantages
The excessive negative pressure applied during the process may cause cellular damage, espe-
cially of more fragile cell types (e.g. lymphoid cells). Excessive haemodilution of the sample
may also occur.
• Technique
Connect the needle to the syringe. Insert the needle within the mass. Apply suction and
redirect the needle multiple times. Discontinue suction before withdrawal. Detach the syr-
inge and draw in some air. Reattach the syringe to needle and expel the sampled material
on to labelled glass slides.
Fine-needle sampling without aspiration
• Advantages
Suitable for sampling skin lesions with good tendency to exfoliate. This technique better
preserves the morphology of fragile cells and minimizes blood contamination.
• Disadvantages
May yield an insufficient cell harvest from poorly exfoliative masses.
• Technique
Insert the needle within the mass and re-direct it multiple times in different areas of the
lesion. Withdraw the needle, attach the syringe containing some air and expel the material
on to labelled glass slides.

© Francesco Cian and Paola Monti 2019. Differential Diagnosis in Small Animal Cytology 11
(F. Cian and P. Monti)