CASE 118
By: Dr. Nizar Al-Nakshabandi MD, FRCPC
HISTORY: 15-year-old boy with right thigh pain.
What are your findings?
What are your findings?
What is the differential diagnosis?
What are the causes?
FINDINGS:
AP & Lateral plain radiograph of right femur (A, B) demonstrate an aggressive mixed lytic-sclerotic lesion arising from the lateral metadiaphysis of the femur, a soft tissue mass is suspected. Periosteal bone reaction is seen, and a positive Codman’s triangle is seen.
Axial T1 fat suppressed (C) weighted image shows diffuse low signal changes involving the distal femur lateral metadiaphysis consistent with tumor infiltration
Axial T2 (D) weighted image shows a mixture of low and high signal changes femur with cortical break present posterolaterally with evidence of tumor involvement in the vastus lateralis muscle. No regional adenopathy. Furthermore, no involvement of the neurovascular bundle.
Coronal T1 (E) shows no evidence of skip metastasis.
DIFFERENTIAL DIAGNOSIS:
· Osteosarcoma.
· Osteomyelitis.
· Metastasis (less likely).
DIAGNOSIS:
Periosteal osteosarcoma.
PEARLS AND DISCUSSION:
An aggressive lesion of the bone.
Tends to affect the diaphysis. Especially femur or tibia.
It is the second most common juxta cortical tumor and affects slightly older patients (10-20).
Always in your differential try to start with the word aggressive rather than malignant. Because osteomyelitis is not malignant, but it is aggressive. Sometimes you cannot differentiate between the two pathologies.
Remember bone tumors are diagnosed by plain radiographs. MRI is a staging tool.
Things you must mention on MR is the signal intensity and its relation to the neurovascular bundle.
Periosteal reaction is present in these tumors in the form of Sunburst or Codman’s triangle.
Mention the presence or absence of regional adenopathy. If present it makes you think of lymphoma of the bone, although bone lymphoma can present itself without regional adenopathy.
Intramedullary extension is rare but occurred in this case.
On MRI these tumors are hypointense on T1, hyperintensity on T2 is related to the chondroid matrix.
The complete work up for any MSK tumor is bone scan, and chest CT. Mention that to the examiner.
Always look for skip metastasis and ask the examiner for a coronal T1 of the whole limb to check for it.
These tumors have an intermediate prognosis, better than conventional osteosarcoma, but not as good as paraosteal osteosarcoma.
FURTHER READING:
1. Murphey MD, Jelinek JS, Temple HT et-al. Imaging of periosteal osteosarcoma: radiologic-pathologic comparison. Radiology. 2004;233 (1): 129-38.
2. Yarmish G, Klein MJ, Landa J et-al. Imaging characteristics of primary osteosarcoma: nonconventional subtypes. Radiographics. 2010;30 (6): 1653-72.
