1. Tumor and Tumor-like Lesion of Bone

2. Osteoma
Osteoma is a benign mass protruding from osseous tissue

3. Osteoma
Most common tumor of the paranasal sinuses, most frequently seen in the frontal sinus and ethmoids
Two varieties are described: the dense 'ivory' type and 'cancellous' osteoma

4. （a) (b)
Osteoma Lateral radiograph of the skull (a) and axial CT scan (b) demonstrate an ossific nodule (arrow) arising from the outer table of the calvarium

5. Giant cell tumor Giant cell tumor is a locally aggressive neoplasm
The sites affected most frequently are the long tubular bones

6. Giant cell tumor Clinical manifestation
Earliest manifestations include pain, local swelling, limitation of motion and pathologic fractures

7. Imaging feature
On radiographs, the long and short tubular bones reveal eccentric osteolytic lesions
With MR imaging, intraosseous fluid levels may be seen

8. Giant cell tumor a, b. AP (a) and lateral (b) radiographs of the knee demonstrate an eccentric osteolytic lesion in the proximal tibia. The lesion has a non-sclerotic border and abuts the articular surface of the tibia.

9. c. Sagittal T1-weighted MR image of the knee demonstrates the low signal intensity mass in the proximal tibia.
d. Fat-suppressed T1-weighted MR image after gadolinium adminstration demonstrates enhancement of the mass in the proximal tibia.

10. Giant cell tumor
osteolytic lesion in the distal radius
soap bubble
expandability
Soft tissue swelling

11. Bone cyst Bone cyst is a usually cavitary lesion of bone.
Bone cysts may occur after trauma and in osteoarthritis

12. These cysts occur most frequently in long tubular bones, especially the metaphysis, and in the bony pelvis

13. Imaging feature
Radiographically, these lesions appear radiolucent and are located centrally, with cortical thinning and mild expansion of the bone
CT scanning and MR imaging with contrast enhancement reveal presence of fluid within the lesion

14. Complications of simple bone cysts include complete and incomplete fractures,
and (rarely) malignant transformation

15. Bone cyst Simple bone cyst
Bone cyst Simple bone cyst. AP radiograph of the shoulder demonstrates a pathologic fracture through the simple bone cyst in the humeral metaphysis.
Note the "fallen fragment" within the bone cyst.

16. Osteosarcoma
Osteosarcoma is a malignant neoplasm of bone composed of proliferating tumor cells that in most instances produce osteoid or immature bone

17. Clinical feature
75% of cases occurring between the ages of 10 and 25 years
86% occur in the long bones with the distal femoral metaphyseal region
The next commonest sites are the upper tibia and humerus

18. Clinical feature
The commonest presentation is pain in the affected area or, occasionally, a pathological fracture
This tumor metastasises early, particularly to the lungs and other bones

19. Imaging feature
On the radiograph, the tumor may be purely lytic or sclerotic , or a mixture of the two

20. Imaging feature
Pure lytic lesions vary from areas of diminished bone density to completely lytic areas with very little reaction from the bone
They may have a very thin periosteal reaction overlying the lesion with very little evidence of new bone formation

21. Imaging feature
The sclerotic osteogenic sarcomas may produce a region of dense sclerosis with loss of the inner cortical margins
The periosteal reaction may be laminated or spiculated with so-called 'sunburst' appearance

22. Imaging feature
More often the tumors are both lytic and sclerotic with destruction of the bone and cortex, and extension into the soft tissues
There may be a variable amount of calcification in the soft tissues
a prominent periosteal reaction with a Codman's triangle

23. MRI:
The lytic areas of the tumor show a low signal on T1 and high signal on T2
The extension in the medullary cavity is very accurately determined by MRI, as is the soft tissue extent

24. Osteosarcoma AP (a) and lateral (b) radiographs of the femur demonstrate a large soft tissue mass with an aggressive periosteal reaction creating the sunburst appearance.
Patchy osteosclerosis and osteolysis in the distal femur

25. Osteogenic sarcoma
Osteolytic sarcoma of the fibular head.
There is a small amount of calcification within the tumor.

26. Osteogenic sarcoma Osteoblastic sarcoma in the upper metaphyseal region of the tibia.
There is sclerosis, breach of the cortex and sclerotic extension of the tumor into the tissues. The cortical margin is lost

27. Osteogenic sarcoma Radiograph of a distal femoral osteogenic sarcoma.
On the radiograph
there is a mixed sclerotic and lytic lesion with a layered periosteal reaction anteriorly and showing calcification.

28. Osteogenic sarcoma
The large soft tissue component is well seen on the MR.
There is high signal within the lesion and in the medullary cavity