MONDO_0015871 (benign breast phyllodes tumor) is a usually unilateral, benign and well circumscribed biphasic neoplasm that arises from the breast. It usually affects middle-aged women. It is characterized by the presence of a double layer of epithelial cells that are arranged in clefts, surrounded by a cellular, monomorphic spindle cell mesenchymal component. Mitoses are rare. Necrotic changes may be present in large tumors. Also known as: benign phyllodes neoplasm of breast, benign phyllodes neoplasm of the breast, benign phyllodes tumor of breast, benign phyllodes tumor of the breast, benign phyllodes tumour of breast, benign phyllodes tumour of the breast, breast benign phyllodes neoplasm, breast phyllodes tumor, benign.