The immunoreactivity of proliferation markers: the Ki-67 antigen and proliferating nuclear cell antigen (PCNA) was assessed, as it has a good prognostic value for chemotherapy response in various tumors (e.g. human and canine mammary tumors, human soft tissue sarcoma, feline lymphoma) [25–27]. The gene discussed is MKI67; the disease is soft tissue sarcoma.