Histourlology of osteosarcoma according to the classification of the World Health Organization in 2002 includes: (1) Common osteosarcoma (accounting for 70 - 75% of cases); (2) Small cell osteosarcoma; (3) Highly malignant superficial osteosarcoma; (4) Telangiectatic osteosarcoma; (5) Secondary osteosarcoma (in Paget, after radiation); (6) Low-grade central osteosarcoma; (7) Paracortical bone sarcoma; (8) Periosteal osteosarcoma.