Our preliminary data obtained in these transgenic mice showed that the HER-2/neu immunization through a protocol which consisted of two administrations carried out in young age (at 6 and 8 weeks of age, standard immunization, SI) delays but not abrogate the spontaneous appearance of mammary tumours, since tumour masses progressively appeared after 40 weeks of age and more than 80% of mice were bearing tumour masses after 90 weeks of age. The gene discussed is ERBB2; the disease is neoplasm.