Burrai et al. tested a different HER2 antibody in canine mammary cancers and found unexpected cytoplasmic immunolabelling on immunohistochemistry (IHC), several bands of inappropriate molecular weights on Western blots, and no HER2 detection by mass spectrometry in any canine mammary tumors that were positive on IHC (63). The gene discussed is ERBB2; the disease is breast cancer.