MSH: A bone tumor composed of cellular spindle-cell stroma containing scattered multinucleated giant cells resembling osteoclasts. The tumors range from benign to frankly malignant lesions. The tumor occurs most frequently in an end of a long tubular bone in young adults. (From Dorland, 27th ed; Stedman, 25th ed),NCI: A neoplasm of bone comprised of osteoclast-like giant cells and mononuclear cells, for which the malignancy status has not been established.,NCI: A benign or malignant bone tumor, usually arising in the end of long bones or the vertebrae. The tumor is composed of round or oval mononuclear cells and uniformly distributed osteoclast-like giant cells. Clinical presentation includes pain, edema, and decreased range of motion in the affected joint.