Age / Sex : 16 / M

Chief complaint: right lower leg pain (onset: 3 months ago)

Osteoblastic osteosarcoma

Discussion

Findings:

Radiograph shows ill-defined sclerosis in proximal fibula with associated periosteal reaction of sunburst type. Soft tissue extension with new bone formation is evident.

MRI shows abnormal bone marrow SI and large extraosseous soft tissue component in proximal fibula with extension into proximal tibia.

Differential Diagnosis:

Lymphoma/leukemia

Blastic metastasis

Ewing sarcoma

Diagnosis: Osteoblastic osteosarcoma

Discussion:

Osteosarcoma is the second most common primary malignant tumor of bone and produces osteoid or immature bone. Conventional osteosarcoma is commonly seen in the second and third decades of life. The presenting symptoms are pain, swelling, restriction of motion, warmth, and pyrexia The typical site is metaphysis of tubular bones in the appendicular skeleton, particularly, femur, tibia, and humerus.

Typical appearance of conventional osteosarcoma include mixed pattern consisting of both osteolysis and osteosclerosis, ill-defined intramedullary lesion extending through cortex and producing a soft tissue mass. Additional findings are periosteal reaction in forms of Codman’s triangle or sunburst pattern and ill-defined cloud tumor ossification/ calcification. MR imaging appears to be superior to other imaging techniques in defining the exact extent of the tumor and identify additional lesions, termed “skip metastasis”

Histologically, osteosarcoma has classically been divided into osteoblastic, chondroblastic, and fibroblastic varieties, depending on the predominant cell type present. Although many lesions

have a mixed histologic appearance, the predominant pattern is osteoblastic in 50%-80% of

osteosarcomas, fibroblastic-fibrohistocytic in 7%-25%, and chondroblastic in 5%-25%.  

References:

1. Bone and Joint Imaging. Resnick 3rd Edition; p1131-1133

2. The Many Faces of Osteosarcoma. Radiographics 1997;17:1205- 1231