Cytology 101

CYTOLOGY 101

Evaluation of a cytologic specimen in small animals with suspected neoplastic lesions often provides a definitive diagnosis, forgoing the need to perform a surgical biopsy. This is particularly true for dogs and cats with superficial neoplasms, intraabdominal masses, hepato- or splenomegaly, or lymphadenopathy. We always evaluate every mass or enlarged organ cytologically prior to performing a surgical biopsy, since the risks and costs associated with a fine needle aspirate are considerably low. In addition, we also routinely evaluate cytologically impression smears of surgical specimens from intraabdominal or intrathoracic masses (ie; intraoperative cytology), and fluids collected by centesis.

Fine Needle Aspiration
With this technique, a single cell suspension is obtained by using a small gauge needle (ie; 23 to 27G) of the appropriate length for the desired target organ/mass, by itself or coupled to a syringe. Tissues easily accessible using this technique include the skin and subcutis, deep and superficial lymph nodes, spleen, liver, kidneys, lungs, thyroid, prostate, and intracavitary masses of unknown origin (eg; mediastinal mass). Once the mass or organ is identified by palpation, radiography, CT, or ultrasonography a needle is then introduced in the mass or organ, piercing it repeatedly (eg;”woodpecker” technique Air is aspirated into the syringe, the needle is coupled, and small portions of the sample are expelled onto glass slides.
Push- or pull-smears are then made and stained with a rapid stain.