The IHC results of this patient’s tumor tissue exhibited ER (+), PR (+), CK7 (+), GATA-3 (+), E-cadherin (+), and GCDFP-15 (+) tumor cells, which, in combination with patient’s breast examination records strongly proved that the gastric lesions were not the primary ones, rather they were breast metastasized secondary lesions. The gene discussed is CDH1; the disease is neoplasm.