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tvpjournal.com | January/February 2016 | Today's VeTerinary PracTice common neoPlasTic skin lesions in dogs & caTs Peer reviewed 29 After expelling the contents onto the sample slide: 1. Use a second slide (smearing slide) to lightly touch the top of the sample, adhering a small amount of sample on its underside (Figure 1). 2. Smear the sample from the smearing slide onto a new slide, using frm pressure to keep the slides touching evenly and fatly as the smear is made (Figure 2). 3. Use the smearing slide to pick up another small bit of sample off the sample slide to smear onto another new slide. 4. Continue until only a very little bit of sample is left on the frst slide, which is then smeared itself. In this manner, at least 3 to 5 good slides are generally produced from one needle sample, allowing for one slide to be stained and evaluated in-house, while other slides can be sent unstained to a clinical pathology laboratory for evaluation. TUMOR CYTOLOGY Mast Cell Tumor Description. Feline mast cell tumors (MCTs) tend to be small, raised, hairless masses, while canine MCTs can grossly look similar to many different lesions, including lipomas and mammary tumors or infections. Diagnosis. Most MCTs are easily diagnosed via cytology (Figures 3 and 4), although a small percentage of canine MCTs have granules that do not stain well with Diff Quik stain (Figure 5,) and must instead have a Wright-Giemsa stain applied (Figure 6, page 30). Thus, keeping some of the cytology slides unstained is key. Management. Feline MCTs typically are easily excised with narrow margins, and often completely FIGURE 2. In the left hand is a new clean slide; the slide in the right hand has been pressed against the top surface of the new slide to apply the sample to the clean slide and then smear it evenly. FIGURE 3. Cytology of a feline MCT; note the numerous round cells with purple staining granules (Diff Quik stain; magnifcation, 20×). FIGURE 4. Cytology of a canine MCT; similar to the feline MCT, this slide has a large number of round cells with varying amounts of purple staining granules (Diff Quik stain; magnifcation, 50×). FIGURE 5. Cytology of a canine MCT showing poorly staining mast cells; scattered red blood cells and cells with segmented nuclei are seen in the background (Diff Quik stain; magnifcation, 20×).