Rationale: Brain metastasis of male breast cancer is extremely rare, and the pathological changes between the primary tumor and the metastatic brain tumor have not been reported. Herein, we report for the first time a case of male breast cancer with metastasis to the parietal lobe with subtype conversion after metastasis. Patient concerns: we describe a 45-year-old male patient admitted for an incidentally found brain tumor after a motorcycle accident. The patient had been treated for breast cancer 5 years previously. The primary tumor was an invasive ductal carcinoma classified as pT1N1M0 wit ...