In this work, the mutational analysis of the feline her2 TK domain, showed that mutations occur in the majority of tumor samples (90%, 36/40), being identified a total of 42 single variants (SVs) (Figure 5), located in introns (54.8%; 23/42) and exons (45.2%; 19/42) (Table S2). The gene discussed is ERBB2; the disease is neoplasm.