Cytology

Samples can primarily be taken as impression smear, scraping or puncture (with or without aspiration). The most common technique is the fine needle aspiration, using a thin hollow needle (G22 – G 27) attached to a syringe. A vacuum is created and, if possible, the tissue should be punctured several times in different directions. Before detaching the needle, the vacuum must be released to avoid the material receding into the syringe. The material obtained is then pressed out of the needle onto the side of a glass slide. A second slide is placed flat at a right angle on top of the first one and is then carefully pulled away across the slide. If the sample is more liquid, a steeper angle (45°) – like in a blood smear – should be applied.

For the cytological examination of puncture fluids, excretions or secretions, the fluids obtained are centrifuged at 2500-3000 rpm for three to five minutes. The supernatant is decanted and the sediment is carefully spread like a blood smear and shipped air-dried. If the puncture fluids are sent directly, EDTA tubes should be used as test vessels.

For bronchial, conjunctival and vaginal cytology, the swab obtained (cytobrush) should be rolled onto a glass slide, not smeared.

All smears should generally be sent in air-dried, but unfixed and unstained. The most important point is to create a thin smear consisting of only one layer (monolayer). The most common reason for getting a limited quality up to not being able to assess at all are smears that are too thick.