In addition to the individual investigation detailed in the present work, the simultaneous occurrence of nsSVs in some haplotypes, that were only detected in cat mammary lesions, could indicate a SV-SV interaction that impacts the effects of the amino acid changes in the 3D structure of the cat erbB-2 protein, which may indicate resistance or susceptibility to breast cancer development and therapy. The gene discussed is ERBB2; the disease is breast cancer.