Perils of immunohistochemistry: variability in staining specificity of commercially available COX-2 antibodies on human colon tissue

We assessed the immunohistochemical (IHC) staining patterns of three commercially available COX-2 antibodies in human tissues. The location of positive stain in sequential serial 4-mu sections of formalin fixed, paraffin embedded tissue differed considerably. Staining patterns ranged from diffuse cytoplasmic to occasional perinuclear staining. Thus, marked variability in staining results from use of different antibodies, making it important to consider the antibody used when comparing reports of COX-2 staining from different investigators.