Figure 5. Squamous cell carcinoma of the mandible in a horse. Negative control slide with pre-immune rabbit serum replacing COX-2 antibody. Note: Minimal weak diffuse background staining in the cytoplasm of both the neoplastic epithelial cells and the adjacent lymphocytes. IHC by Dr. Sheree Beam for Dr. K. Rassnick lab, Dept. Clinical Sciences.