Cystosarcoma phyllodes (CSP) tumour. This is also known simply as a phyllodes tumour as about 90% of them are in fact benign, despite its sarcoma suffix. It is a rare neoplasm, accounting for just 1% of all breast cancers. They usually occur before menopause, typically in women in their fourth decade. They arise from hypercellularity of the intralobular stroma of the breast, and impact upon the epithelium surrounding them to produce a leaf-like appearance. They differ from the most common breast neoplasm fibroadenomas as they do not involve the glandular part of the breast tissue i.e. the milk-producing part. They are treated surgically with a wide-local excision, and often extra healthy tissue is removed too as they are prone to recurrence.