Review Question - QID 4588

Based on the radiographs and biopsy shown, the patient has a diagnosis of osteosarcoma.

Osteosarcoma is the most common primary sarcoma of bone, occurring in children and young adults. The proximal tibia and distal femur are most commonly affected. At the time of diagnosis, osteosarcomas are often high grade, extra-compartmental and without evidence of metastases. The mainstay of treatment for high grade osteosarcoma is neo-adjuvant chemotherapy, limb salvage resection followed by post-operative chemotherapy.

Messerschmitt et al. review the evaluation, diagnosis and management of osteosarcoma. In cases of localized osteosarcoma, use of chemotherapy and limb salvage resection have improved survival rates to 60-78%. The role of preoperative of chemotherapy is to aid in decreasing the neo-vascularity of the tumor, thereby decreasing the tumor burden. Surgical resection often occurs three to four weeks after the last preoperative dose of chemotherapy.

Figures A and B show an intramedullary osteosarcoma within the tibia. There is blastic involvement of the metaphysis within the lateral aspect of the tibial metaphysis. Figure C shows the histology of an intramedullary osteosarcoma. Note the cellular atypia and presence of multi-nucleated giant cells.

Incorrect Answers:
Answer 1: Ewing's sarcoma is a small blue cell tumor with an associated t (11:22) translocation
Answer 2: Eosinophilic granuloma is a benign process characterized by Langerhans cells, inflammatory cells and absence of nuclear atypia.
Answer 3: Lymphoma is a hematopoietic malignancy characterized by small round cells and diffuse infiltration of trabeculae.
Answer 5: Osteoblastoma is a benign tumor that is characterized by a nidus comprised of immature osteoid and osteoblasts. This is distinct from reactive bone. Multiple giant cells are also seen.