Benign Bone-Forming Tumors Osteosarcoma: Old and New Challenges Benign Cartilage-forming Tumors Malignant Cartilage-Forming Tumors Notochordal Tumors Vascular Tumors of Bone: Updates and Diagnostic Pitfall Intra-Articular Tumors Undifferentiated Small Round Cell Sarcomas of Bone Giant Cell-Rich Tumors of Bone Fibrous and Fibro-Osseous Lesions of Bone Osteofibrous Dysplasia and Adamantinoma Miscellaneous Tumours of Bone