ERBB2 and breast carcinoma: In order to extend previous studies on ACKR2 in carcinogenesis, we crossed Balb/c Ackr2−/− mice with Balb/c NeuT mice, which overexpress the rat Her2/neu oncogene under the mouse mammary tumor virus promoter and spontaneously develop mammary carcinomas closely recapitulating human breast carcinogenesis19.