A benign, circumscribed fibroepithelial neoplasm arising from the breast and rarely the prostate gland. It is characterized by the presence of epithelial structures which are arranged in clefts and by a hypercellular mesenchymal stroma which is organized in leaf-like structures. There is no evidence of cellular atypia or sarcomatous features. The disease is Monarch Disease Ontology id MONDO_0037002 (benign phyllodes tumor). Also known as: benign cystosarcoma phyllodes, benign phyllodes neoplasm, phyllodes tumor, benign.