What is phyllodes tumor (cystosarcoma phyllodes)?

Updated: Jul 20, 2021
  • Author: Donald R Lannin, MD; Chief Editor: John Geibel, MD, MSc, DSc, AGAF  more...
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Phyllodes tumor—once more commonly referred to as cystosarcoma phyllodes (from Greek kystis ["sac, bladder"], sarkoma ["fleshy tumor"], and phyllon ["leaf"])—is a rare, predominantly benign tumor that occurs almost exclusively in the female breast. [1, 2] Grossly, the tumor displays characteristics of a large, malignant sarcoma, takes on a leaflike appearance when sectioned, and displays epithelial, cystlike spaces when viewed histologically.

Because most of these tumors are benign, the term cystosarcoma is potentially misleading. Accordingly, the term currently favored is phyllodes tumor.

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