Findings: A lateral view of the skull demonstrates a mixed lytic and sclerotic lesion within the right frontal bone with relatively well-defined sclerotic margins.

An axial CT image through the skull and bone windows demonstrates an expansile mass within the right frontal bone with thickening of the outer table. Calcified matrix is also identified. No definite intracranial extension is seen.

Diagnosis: Chrondrosarcoma.

Discussion: Chrondrosarcoma affects patients between the ages of 30 and 60 years with pain being the most common presentation. They may occur as primary bone tumors or develop from a pre-existing lesion such as an enchondroma. Pain is a distinguishing feature between enchondromas and chondrosarcomas.

Chondrosarcomas most commonly arise in the long bones, most frequently within the femur. Other locations include the ribs, vertebrae and scapula.

Radiographically, a large osteolytic lesion can be seen. Organized calcific rings may suggest a low-grade tumor. Alternatively, an irregular calcified matrix may suggest a high-grade chondrosarcoma.

Reference:
Resnick D. Bone and Joint Imaging, 2nd Edition.
W.B. Saunders, Philadelphia; 1996:1021-1026.

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