SPP1 and rhabdomyosarcoma: In contrast, the three remaining patient groups with a high serum (>516.54 ng/ml) and tumor (>34.34 ng/mg) OPN protein level were composed of more than 80% of patients with malignant fibrous histiocytoma (MFH), fibrosarcoma (FS), leiomyosarcoma (LMS), rhabdomyosarcoma (RMS).