• Rare, low-grade, malignant tumor
• Most common in 20- to 40-year-olds
• Generally found in epiphysis or metaphysis of long bone, particularly proximal femur and humerus
• Radiographic presentation:
  • Geographic osteolytic lesion at end of long bone
  • Cortex generally intact, but may be expanded
  • Often has sharp sclerotic margins; exception: larger lesions, which may have indistinct margins
  • Calcification within lesion uncommon
• Microscopic presentation:
  • Admixture of clear cells, chondroid matrix, and giant cells
  • Ossification may be present
• Tumor may resemble a benign tumor radiologically (such as chondroblastoma); however, can metastasize and must be treated with wide resection