Most patients are between 13 and 17 years of age

Second smaller peak of incidence after 65 years of age, often as secondary cancer

Rare younger than 6 years of age

Persistent bone pain; symptoms for 3 to 6 months

Metaphyseal, eccentric (90%)

Diaphyseal less common (5% to 10%)

Distribution: approximately 70% in long bones, more than 50% about the knee; frequency is (1) distal femur, (2) proximal tibia, and (3) proximal humerus

Lytic portions typically have nongeographic margins

Cortical destruction

Soft tissue mass seen in the majority of cases (80%)

Osteoid matrix

Minority of tumors demonstrate little or no visible mineralization on radiographs

Osteoid matrix, appearing as “fluffy” or “cloudlike” opacification ( left and right ).

Note mineralizing soft tissue mass on left ( arrow ). Note the aggressive, “hair-on-end” ( arrow ) periosteal reaction ( right ).

Many lesions demonstrate mixed lysis and sclerosis, representing osteoid matrix ( left and right ).

A pathologic fracture through an osteosarcoma ( left ); 5% to 10% of lesions have a diaphyseal location.

Absence of matrix is seen in a minority of lesions, as in this proximal humerus lesion ( right ). A wide zone of transition is seen in all lesions.

Bone scan of a proximal tibia tumor shows intense uptake ( left ). Note the less intense uptake in the ipsilateral distal femur and ankle due to disuse osteopenia and hyperemia.

Fused PET/CT scans of a proximal humerus tumor showing hypermetabolic activity in both bone and soft tissue components ( right ).

CT scans demonstrate dense osteoid matrix in proximal tibia ( left ) and proximal humerus lesions ( right ).

The humerus lesion also shows less mineralized posterior soft tissue component ( arrow ).

T1 ( left ) and T2 ( right ) MRIs are useful in demonstrating the extent of marrow replacement and extraosseous tumor involvement ( right ).

Note the typical absence of prominent surrounding soft tissue and marrow edema ( right ).

Most metaphyseal lesions (75% to 90%) extend across the epiphyseal plate, as seen on T1 ( left ) and T2 ( right ) MRIs.

The most common appearance on T2-weighted sequences is high intensity ( right ).