A 42-year-old woman presented with a rapidly growing tumor of the breast accompanied by anemia (7.4 g/dL), hypoalbuminemia (1.6 g/dL), and increased alkaline phosphatase (256 U/L). Magnetic resonance imaging of the breast demonstrated a heterogeneous mass composed of verrucous solid components with hemorrhagic areas. There was no evidence of cachexia, and the metastatic workup was negative. Final pathology revealed a 22-cm malignant phyllodes tumor. Hypoalbuminemia and alkaline phosphatase quickly resolved after surgical excision without any further treatment.