Lymph nodes are typically aspirated in cases of unexplained lymphadenomegaly, where lymphoproliferative disease is suspected, and to assess for the presence of metastatic non-lymphoid neoplasia. Where multiple nodes are enlarged, it is preferable to sample several affected nodes. Up to six cytology slides may be submitted in total from affected nodes. Submandibular lymph nodes tend to be more reactive and often yield inconclusive results, therefore is is not recommended to aspirate only these nodes.
Immunocytochemistry for B and T cell phenotyping (canine and feline only) may now be performed on cytology slides if they are of sufficient quality (meaning there is a monolayer of well-preserved lymphocytes), for additional cost.
Aspirated material on glass slides, air-dried, stained or unstained
Glass slides, slide container
Use a 21-22 gauge needle alone (“woodpecker” technique - insert and withdraw the needle multiple times). A smaller gauge needle may lyse the cells (neoplastic lymphocytes are quite fragile) and a large needle may result in excessive blood contamination. Expel the aspirated contents onto the top 1/3 of a clean glass slide. Then take another slide, gently place it on top. Do not apply pressure, but use only the weight of the slide to spread out the material. Gently pull the slides along each other lengthwise until they separate. This will result in two slides with a monolayer of cells. Air dry slides.
If in-house stains are performed, it is preferable to also submit unstained slides.
Special Handling/Shipping Requirements:
Place slides in slide-containers for shipment. Do not ship with samples containing formalin (wrap and bag separately). Formalin fumes prevent cellular uptake of differential stains, rendering the slides non-diagnostic. Do not store cytology slides in the fridge, as condensation will render the slides non-diagnostic.