Review Question - QID 106077

The clinical presentation, radiographs, and pathology are consistent with a diagnosis of osteosarcoma.

Osteosarcoma is an osteogenic malignancy which usually occurs in children and young adults. The most common site of involvement is the distal femur and proximal tibia. Pain is usually the primary symptom, and the presence of fever is variable. Laboratory studies are characterized by a markedly elevated alkaline phosphatase. Treatment is multi-agent chemotherapy and limb salvage resection.

Figure A is a plain films showing a mixed lytic/blastic destructive lesion in the distal femur. Figure B is a pathology specimen that shows pleomorphic osteoblastic cells and lacey osteoid.

Incorrect Answers:
Answer 2: Osteoblastoma is a benign osteogenic tumor that occurs in young adults. Histology is characterized by a distinct demarcation between nidus and reactive bone, and does not show the malignant features seen in this case.
Answer 3: Paget's disease is a condition of abnormal bone remodeling. Histology shows irregular broad trabeculae with disorganized cement lines.
Answer 4: Osteomyelitis is often confused with osteosarcoma. Histology and clinical presentation is most important to differentiate the two.
Answer 5: Chondrosarcoma is chondrogenic malignant tumor characterized by hypercellular stroma consisting of characteristic "blue-balls" of a cartilage lesion which permeate the bone trabeculae on histology.