Phyllodes tumors are rare breast neoplasms. Surgery is the treatment of choice. The role of postoperative radiotherapy and chemotherapy is still under dispute, as there are no equivocal prognostic factors. Treatment failure results in the occurrence of distant metastasis—mainly to the lungs, bones, liver, and brain. We have described the case of a woman with a malignant phyllodes tumor of the breast that was surgically treated. She did not receive adjuvant therapy because there is no consensus on the role of postoperative chemotherapy and radiotherapy. One year following the surgery, the patient had left-sided nephrectomy performed because of a rapidly growing tumor of the kidney. Renal cancer was suspected; however, a histopathological examination revealed that it was a metastatic phyllodes tumor. At the same time, the patient was diagnosed as having metastases in the other kidney, the lungs, liver, and bones.Our case report describes not only an unusual localization of the metastases (in the kidneys), but also failure of the chemotherapy and the aggressive course of malignant phyllodes tumor. Identification of patients with high risk for distant metastasis and the introduction of uniform rules for the management of adjuvant chemotherapy and radiotherapy would make planning treatment as efficacious as possible.