- 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
Pediatric Imaging 