malignant phyllodes tumor (MONDO_0037003, a Monarch Disease Ontology entry) can be described as follows. A phyllodes tumor with sarcomatous stroma. The sarcomatous component is usually of the fibrosarcomatous type. Liposarcomatous, chondrosarcomatous, osteosarcomatous, or rhabdomyosarcomatous differentiation may also occur in the stroma. It may recur and metastasize following surgical resection. The lung and skeleton are the anatomic sites most frequently involved by metastases. Also known as: malignant cystosarcoma phyllodes, malignant phyllodes neoplasm, phyllodes tumor, malignant.