The median OPG expression level was 3731 (range, 1128–28,413) for FD, 2683 (range, 2069–6643) for chordoma, 2210 (range, 107–14,942) for chondrosarcoma, and 1657 (range, 149–16,049) for osteochondroma (Fig 3). The gene discussed is TNFRSF11B; the disease is chondrosarcoma.