40Complications of polyostotic Paget disease; histologically similar to primary osteosarcoma Cartilaginous BENIGN 1.Osteochondroma (most common benign bone tumor)Metaphysis of long tubular bones10-30Bony excrescences with a cartilaginous cap; may be solitary or multiple and hereditary2.ChondromaSmall bones of hands and feet30-50Well-defined single tumors resembling normal cartilage; arise with medullary cavity of bone; uncommonly multiple and hereditary MALIGNANT 1.ChondrosarcomaBones of shoulder, pelvis, proximal femur, and ribs40-60Arise within medullary cavity and erode cortex; microscopically well differentiated cartilage-like or anaplastic; Miscellaneous 1.Giant-cell tumor(usually benign)Epiphysis of long bone20-40Lytic lesions that erode cortex; microscopically, contain osteoclast-like giant cells and round to spindle-shaped mononuclear cells; majority are benign2.Ewing tumor(malignant)Diaphysis and metaphysis10-20Arise in medullary cavity; microscopically, sheets of glycogen-rich small round cells; aggressive neoplasm3.Chordoma(Locally malignant)Axial skeleton (Sacrococcygeal bones, Clivus, cCervical vertebra)20-40Expansile lytic tumor."Physalliferous cells" +">