Ewing sarcoma is the second most common type of bone tumor (after osteosarcoma) in children and adolescents. The tumor is usually a lytic bone lesion, and often both invades the medullary cavity of the bone and extends into extraosseous tissues. Grossly, the tumor is often tan-white in color and shows focal areas of hemorrhage and necrosis. Microscopically, it is composed of sheets of small, round cells with scanty cytoplasm that may appear clear because of their glycogen content. Chondrosarcoma is composed of malignant hyaline and myxoid cailage. Giant cell tumor of bone contains multinucleated giant cells in a background of mononuclear stromal cells. Malignant fibrous histiocytoma has a background of spindled fibroblasts in a storiform pattern admixed with bizarre, multinucleated tumor giant cells.