In infiltrating ductal carcinoma samples that metastasized to lymph node, however, we observed that a significant portion of the samples displayed mutually exclusive staining patterns for EphA2 and ephrin-A1 (p<0.05, Chi square analysis; n = 32 total lymph node metastastic samples, 2 ephrin-A1+/EphA2+ versus 9 ephrin-A1+/EphA2− and 8 ephrin-A1−/EphA2+). This evidence concerns the gene EPHA2 and invasive ductal breast carcinoma.