ERBB2 and breast cancer: GM from breast cancer occur in approximately 10% of all metastatic cases, with few reports on male breast cancer.25) The reported case we identified involved hormone receptor-positive and HER2-positive IDC, whereas our case presented as hormone receptor-negative and HER2-positive ILC.26) It is known that GM are more commonly derived from lobular carcinoma than from ductal carcinoma.5) Furthermore, a significant difference between the reported case and the present case is that the present case involved male OBC.