However, contrary to the situation in humans, where 85% to 90% of breast carcinomas with HER-2 protein overexpression have a higher number of copies of the oncogene HER-2, a low percentage of feline carcinomas with HER-2 protein overexpression (16.6%) presented a number of HER-2 copies in the limits of what can be considered gene amplification. This evidence concerns the gene ERBB2 and breast carcinoma.