MONDO_0002618 (undifferentiated high grade pleomorphic sarcoma of bone) is a rare, high-grade pleomorphic malignant neoplasm arising from the bone. It usually presents with pain which may or may not be associated with swelling in the affected area. It is characterized by the presence of spindle-shaped cells, polygonal or epithelioid cells, multinucleated giant cells, and inflammatory cells. The neoplastic cells exhibit nuclear pleomorphism and high mitotic activity. It metastasizes frequently, most often in the lungs. Also known as: malignant bone fibrous histiocytoma, malignant fibrous histiocytoma of bone, malignant fibrous histiocytoma of the bone, undifferentiated high grade pleomorphic sarcoma, undifferentiated high-grade pleomorphic sarcoma.