Recently, some reports have shown that the feline homologue of human epidermal growth factor receptor-2 proto-oncogene (HER2) is overexpressed in 33%-60% of FMC [10, 13, 14, 15] and it was associated with a shorter overall survival (OS) [14] as in human HER2 positive breast tumors, even though the HER2 gene amplification could not be detected [10, 13]. This evidence concerns the gene ERBB2 and breast neoplasm.