Monarch Disease Ontology entry MONDO_0006287 (malignancy in giant cell tumor of bone) can be described as follows. A malignant tumor that arises from the bone. It is characterized by the presence of an area of high grade sarcoma in an otherwise typical giant cell tumor (primary malignancy in giant cell tumor), or the presence of sarcoma in which the pre-existing giant cell tumor may or may not be apparent (secondary malignancy in giant cell tumor). Also known as: Dedifferentiated giant cell tumor, Dedifferentiated giant cell tumour, OSTEOCLASTOMA, malignant, bone giant cell sarcoma, giant cell bone sarcoma, giant cell sarcoma of bone, giant cell sarcoma of the bone, giant cell tumor of bone, malignant.