Cystosarcoma phyllodes (a phyllodes tumour) is a rare form of breast tumour. It is often benign but may be malignant. It arises from a fibroadenoma in the breast. The tumour takes its name from its leaf-likestructure as seen under a microscope. The word phyllodes means leaf in Greek.
Affected women have a firm breast lump that enlarges rapidly to several centimetres in diameter. Mammography (breast x-ray) and ultrasound may be used initially in investigation. In most cases a needle biopsy is necessary to confirm the diagnosis.
The tumour is surgically excised with a wide margin of normal tissue. With very large tumours, this may require a mastectomy (breast removal). Recurrence is common after excision and rarely the tumour may become cancerous.