Diagnosis and treatment of low-grade osteosarcoma: experience with nine cases Katsuhiro HayashiHiroyuki TsuchiyaNorio YamamotoToshiharu ShiraiHideji Nishida • Akihiko TakeuchiHiroaki KimuraShinji MiwaHiroyuki InataniHideki OkamotoSatoshi Yamada • Hiroko IkedaSeiko Sawada-KitamuraTakayuki NojimaAkishi OoiTakanobu Otsuka

Background Low-grade osteosarcoma, including lowgrade central osteosarcoma and parosteal osteosarcoma, is an extremely rare variant, and the diagnosis is occasionally difficult. In this article we present cases of low-grade osteosarcomas that should be reviewed by a clinical oncologist. Patients and methods Nine cases of histologically diagnosed Broder grade 1 osteosarcoma were retrospectively reviewed. The pathological diagnoses included parosteal osteosarcoma, low-grade central osteosarcoma, and lowgrade chondroblastic osteosarcoma in four, four, and one cases, respectively. Results Duration from initial surgical intervention including biopsy to final diagnosis as low-grade osteosarcoma was a mean of 9.4 months. The initial benign diagnoses on biopsy specimens included fibrous dysplasia in three cases, chondroblastoma in one case, and a giant cell tumor in one case. The average number of histological examinations was 1.8. Low-grade osteosarcomas are well suited for biological reconstruction: seven cases were reconstructed by frozen autografts, distraction osteogenesis, or vascularized bone grafts.