Phyllodes tumor is a rare breast tumor.A 45-year-old woman who underwent left mastectomy 12 years ago was found to have infiltrates in both lungs in a health examination.Combining histological examinations of the lung and breast samples,the diagnosis of borderline phyllodes tumor metastases to the lung was made.It is the longest interval to our knowledge that the metastases occurred 12 years after primary phyllodes tumor.