CASE 76

By: Dr. Amna Kashgari MD,SSC-Rad

HISTORY: 12-year-old boy presented with pain in his left knee.

What are your findings?

What is your differential diagnosis?

What is your most likely diagnosis?

What are the major known clinical association?

FINDINGS:

Frontal (A) and lateral (B) plain radiographs of the left knee show a sclerotic lesion of the distal femoral metaphysis. The lesion shows a wide zone of transition with associated exuberant “sun ray” periosteal reaction. No pathological fracture is noted. No joint effusion.

DIFFERNITAL DIAGNOSIS:

• Osteosarcoma.

• Ewing sarcoma.

• Metastasis (less likely).

DIGNOSIS:

Osteosarcoma.

PEARLS AND DISCUSSION:

Osteosarcoma is the most common primary malignant bone tumor in adolescents and young adults. It accounts for approximately 15% of all primary bone tumors.

Location

They typically occur at the meta-diaphysis of tubular bones in the appendicular skeleton.

Common sites include:

• Femur: 40% (especially distal femur).

• Tibia: 16% (especially proximal tibia).

• Humerus: 15%.

Other bones maybe affected

Plain radiography is almost diagnostic. Nevertheless, MRI is essential for local staging and assessment for limb salvage surgery, and soft-tissue involvement. Assessment of the growth plate is also essential as up to 75-88% of metaphyseal tumours do cross the growth plate into the epiphysis.

It is very important to plan the biopsy tract with the treating surgeon to reduce the change of seeding during surgical resection, which potentially require extensive surgery with poor outcomes.

Types of the disease:

• Intramedullary osteosarcoma.

• Surface osteosarcoma.

• Extra skeletal osteosarcoma.

FURTHER READING:

1. Lane F Donnelly. Fundamental of pediatric radiology. ISBN-13: 978-0721690612

2. Johan G Blickman, Bruce R Parker, Patrick D Barnes. Pediatric Radiology: The Requisites, 3e. ISBN-10: 0323031250