Surface Osteosarcoma

  • Parosteal osteosarcoma
    Etiology: malignant bone forming tumor arising from outer periosteum
    Imaging:
    — Location: posterior distal femur (62%)
    — Lytic or blastic:
    — Matrix: fibrous
    — Zone of transition: (wide, narrow)
    — Periosteal new bone or cortical destruction:
    — Additionally: attached to underlying cortex, lobulated exophytic mass, string sign in 30%, medullary extension in 50%
    Clinical: most common surface type (5% of osteosarcomas), older 20-50 years old, low grade
  • Periosteal osteosarcoma
    Etiology: malignant bone forming tumor arising from inner periosteum
    Imaging:
    — Location: diaphysis, tibia
    — Lytic or blastic:
    — Matrix: chondroid
    — Zone of transition: (wide, narrow)
    — Periosteal new bone or cortical destruction: periosteal reaction and cortical erosion
    — Additionally: cortical thickening, no medullary involvement
    — Radiograph: broad-based, soft-tissue mass, periosteal reaction, cortical erosion, thickened underlying cortex
    — CT: low density chondroid matrix
    — MR: may be hypointense on T1WI + T2WI, may have high T2 signal chondroid matrix, limited reactive marrow changes
    Clinical: least common surface type (1.5% of osteosarcomas), 15-25 year old, intermediate grade

Radiology Cases of Surface Osteosarcoma

Radiology Cases of Parosteal Osteosarcoma

Radiograph of parosteal osteosarcoma of the femur
AP and lateral radiographs of the left hip shows a poorly circumscribed, sclerotic, expansile lesion that appears to be attached to the cortex.

Radiology Cases of Periosteal Osteosarcoma