Abstract： To the Editor:Phyllodes tumors are rare fibroepithelial malignancies of the breast and account for ＜ 1％ of all malignant breast tumors.[1] It is difficult to distinguish from fibroadenomas,while malignant cystosarcoma phyllodes can grow in size quickly and metastasize early.[2] Gigantic cystosarcoma phyllodes of the breast is very rare,thus limiting our understanding of the disease and influencing diagnostic and management outcomes.Here,we reported a case of pulmonary metastasis of a gigantic cystosarcoma phyllodes of the breast with a maximum diameter of nearly 15 cm.