By cellular origin: tumor cell phenotype and type of mesenchymal production Cartilage origin: osteochondroma, chondroma, chondroblastoma (chondroblastoma-forming tumor), chondrosarcoma Bone origin: osteoma, bone-like osteoma, osteoblastoma (osteoblastoma), osteosarcoma Fibrous origin: benign fibrous histiocytoma, nonossifying fibroma, fibrous structural dysplasia, fibrosarcoma, malignant fibrous histiocytoma Hematopoietic origin. Myeloma, lymphoma Vascular origin: hemangioma, lymphangioleioma, hemangiosarcoma, malignant hemangiopericytoma Fatty origin (rare): intraosseous lipoma, intraosseous liposarcoma Chordal origin: chordoma Other: bone cyst, aneurysmal bone cyst, eosinophilic granuloma, giant cell tumor of bone, Ewing’s sarcoma By etiology: primary Secondary Metastatic By tumor biology: benign Commonly occurring are osteochondroma, endogenous chondrosarcoma, osteoid osteoma, giant cell tumor of bone, fibrous dysplasia, etc. Malignant common ones are osteosarcoma, chondrosarcoma, malignant fibrous histiocytoma, Ewing sarcoma/primitive neuroectodermal tumor (PNET), myeloma, malignant lymphoma, etc. Neoplastic lesions commonly include bone cysts and eosinophilic granulomas.